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Full text of "73 Magazine (March 1967)"

MARCH 1967 
A windy 60c 



AMATEUR RADIO 



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73 Magazine 



Wayne Green W2NSD/I 
Publisher 

Paul Franson WAICCH 
Editor 

Jim Rsk WIDTY 
Technical Editor 

Jack Morgan KIRA 
Advertising Manager 

March 1967 
Vol. XLVL No. 3 

Cover by Wayne Pierce K3SUK 



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73 Magazine is published month) j 
by 73, Inc., Peterborough, N. EL 
03458. The phone is 603-924-3873. 
Subscription rate: $5.00 per jear, 
$9.00 two years, $12*00 three years. 
Second class postage is paid at 
Peterborough, New Hampshire and 
at additional mailing offices. Printed 
in Pontiac, Illinois, U.S.A. Entirs 
contents copyright 1067 by 73, Inc. 
Postmasters, please send form 3579 
to 73 Magazine, Peterborough, N«w 
Hampshire. Watch for the Special 
April Issue. It'll be full of fun. 



A Digital Identification Generator _ . _K6ZCE A 

Send your call automatically with no moving ports* 

SSB Proof of Performance ™_„.K6YKH _.„„„ 14 

How does your station perform? 

A Non-Tiring CW Monitor rt „WlDCG„._ 18 

Pure single sine waves are monotonous. Try this instead. 

Seven Elements on Twenty .,„„. WA4WWM 20 

On a 60 1 boom. 

Climbing the Novice Ladder W7QE „. 24 

Part IV: The code is almost conquered. 

Going RTTY: Part IV . r W4RWM 30 

Frequency shift keying. 

A Solid-State Product Detector _ JvVB6CHQ___„„. 32 

Uses two cheap transistors* 

AMCOM: Amateur Mobile Communications M K3CEE.. ... 36 

The Phil-Mont Radio Club's emergency stations. 

The Slide Rule Made Easy „„ _ __ WlMEG 40 

It is easy, too. 

How to Make Better Panels . W2DXH 46 

Jim's suggestions wort. I tried them. 

Here's a different integrated circuit keyer. 

Edison: The Fabulous Drone „„.„. Elkhorne 52 

Was Edison really a greet genius? 

A Simple RF Voltmeter . ™ WlDTY 56 

Make a very useful piece of test equipment. It's low 
in cost. 

SDRAWKCAB Power Supply . KlUBA_.._™ 62 

Guess what this Is? 

A Panadapter Converter ., it .WB2CCM 64 

It helps you get decent patterns on your panadapter. 



SPECIAL BOOK-LENGTH FEATURE ARTICLE 

73 Useful Transistor Circuits „. WIDTY..- 

If you're a builder, you'll like this one* It's a fantastic 
collection of useful, simple circuits using transistors for 
all sorts of receiving, transmitting and test equipment. 
It's 32 pages long. 



- 65 



The Importance of Being Grounded „ 

It is important, 

Gus: Part 21 , — 

This month, Gus visits darkest Africa, 



.WA6KLL 



98 



W4BPD -100 



The Waters Dummy Loads 

One Is plain j the other a wattmeter. 



IIIIIH i irafcitin I v I I . 



106 



De W2NSD . 



mmm-mmm^M 



Editor's Ramblings .,„^,..,„ 
WTW News _.„ 



I ■ I L I 1 ■ 1 I ■■■»*• 



What's New „ 



H*«*»«#j*aM*BBW1 



2 

. . 4 

107 

112 

I ■■■■■■■ I 1 »■ 



Propagation 



117 



New Product .-_ ~ ~H8 

Caveat Emptor .■■.■■.■■■■..■ — 122 



Technical Aid Group , — „.„„., — 116 Index to Advertisers ™„ 126 



MARCH 1967 



mmmm 



de 
W2NSDI1 



n©ver say die 



I see that ARRL is still leaving no stone 
unturned to try and kill off the Institute of 
Amateur Radio. They've done their usual 
thorough job of making sure that the League 
is the only national amateur organization. 
Not that the Institute is dead, by any 
means, it's just a definite unsuccess. 

The responsibility for the failure of the 
Institute to succeed is largely mine. I know 
when I started it that it would be fought by 
every means possible by the ARRL and I 
was sure that CQ would be as truthful as 
usual in reporting about it. Rut I am an 
incurable idealist and somehow convinced 
myself that enough amateurs would be in- 
terested in helping to keep amateur radio go- 
ing to overcome the barrage of lies and dis- 
tortions. 

Let me go back and explain. As one of 
the three officially recognized amateur radio 
delegates to the 1959 ITU conference I had 
an opportunity to see at first hand the work- 
ings of that organization. I was incredulous 
that amateur radio went into that conference 
almost totally unprepared. I felt that we 
had been deceived and completely failed by 
the ARRL. I watched the two League repre- 
sentatives living it up in millionaire style , . . 
they managed to spend over $15,000 of the 
ARRL funds in just a few weeks. The com- 
plete failure of the League to get support 
for amateur radio, even within the U.S. 
delegation, was incredible, I talked with the 
other members of our delegation to find out 
what had gone wrong and what could be 
done to see that this didn't happen again. 

I'm afraid that they all thought 1 was 
vrry naive . , . and I guess I was. J had not 
recognized fust how important Washington 
was until then. This is where everything 
conies to a head , . . this is where it happens. 
Each of these gentlemen explained patiently 
to me that amateur radio was at the very 
ho l torn of their list as far as priority in 
frequency allocations was concerned and 
that it would remain that way as long as 



we did not pressure where it counts : on Con- 
gress. 

They pointed out that every other major 
user of radio frequencies maintains a lobby 
in Washington to look after their interests. 
They wondered if I thought that all this 
money would be spent on lobbies if they 
weren't well worth the investment? Then 
they brought up the fact that every other 
major hobby group looks after the interests 
of their field by having a voice in Washing- 
ton, I certainly can't argue the effectiveness 
of the American Rifle Association, the Air- 
craft Owners and Pilots Association, and 
many others. 

Amateur radio, they laughed, has no voice 
in Washington. But what about the League 
counsel in Washington? No, son, this gentle- 
man can only represent the ARRL in deal- 
ings before the FCC and cannot, by law, 
approach any Senators or Congressmen in 
behalf of the League. No, if the League were 
to lobby for amateur radio in any way they 
would have to give up their tax-free setup 
and operate as a regular business. The law 
just does not permit tax-free organizations 
to try to influence legislation. 

If a voice in Washington is of such great 
importance, why is it, I asked, that the ARRL 
doesn't give up its tax-free situation and do 
the job that will protect our future? They 
are the obvious ones to be lobbying for 
amateur radio- The answer was dollars, of 
course. Loss of the tax-free government sub- 
sidy of the League might cost them well over 
$100,000 a year, forcing them to either in- 
crease the subscription rates to QST or else 
cut down on the number of high salaries 
being paid. Neither course is desirable so we 
have no lobbying permitted by the League. 

By 1963, 73 had reached a size where I 
thought we might be able to get something 
started to fill in this lobby gap in amateur 
radio. Time seemed to be growing short too, 
for in 1959 the USSR came to our rescue and 
put off the changes in our frequencies until 
the next ITU conference and this seemed to 
be headed for us in the late 196G's, leaving 
not much time for building up support both 
within the U.S f and internationally* The In- 
stitute of Amateur Radio was formed with 
the major job of lobbying for our hobby in 
Washington. 

It was never the purpose of the Institute 
to compete with the ARRL as an alternate 
organization for amateurs to join. The In- 

{Cmtinntd on pagt 114) 



73 MAGAZINE 




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— 



Editor's Rambling* 



Paul Franson WAlCCH 



Special features 

Have you looked through this 73 yet? If 
not, thumb through quickly. We've got a 
special feature for you in this issue. It's the 
Ik >ok (let) -length article, '73 Useful transis- 
tor Circuits." Jim Fisk W1DTY has spent a 
lot of time and work on this feature; from 



the looks of the results, the time was well 
spent, for he's done an excellent job. It will 
be a rare ham who doesn't consult this sec- 
tion often in his building. If you like it, be 
sure to drop Jim a line. I suspect that he's 
got at least 73 more circuits that he could 
use to make "73 Transistor Circuits part 
II." In fact, he'd probably like to have your 
suggestions and contributions for part IL 

Our book-length features have been very 
popular; and we look forward to publishing 
many more. If you have any suggestions for 
topics, be sure to let us know. And don't 
forget that we're in the market for book- 
length manuscripts. If you have the time and 
ability, and would like to work on one, 
please write me with an outline of what 
you'd like to write about Preparing a manu- 
script of this type is a lot of hard work, but 

ry rewarding in both personal satisfaction 
and in t lie payment. 

Special issues 

Next month's issue is our April special. 
This April, we've got a double bonus for 
you. First, we'll have a sideband section. It 
will contain a listing of all commercially 
available HF SSB transceivers, transmitter 

rivers and linear amplifiers. If you're 
thinking about buying some sideband gear, 
reading this section is a must! You'll want 
to study the specifications, descriptions, 
photographs and comparisons of all the gear. 
In fact, you'll have a strong will if you 
don't rush to your dealer or mail in an order 
for some new equipment after reading it. 



The second special feature in April is too 
horrible for words and too secret to divulge* 
We can't let the rat out of the bag yet, but 
we will warn you: Be Prepared* It's even 
worse than last April's Playboy spoof. I sus- 
pect that 777 people will cancel their sub- 
scriptions after seeing it, 

Our May issue will be devoted to quads. 
Amateur interest is very high in these ex- 
cellent antennas, and we've get many good 
articles about them. They range from a full- 
M/e quad for forty to a quad-quad-quad for 
\ HF. We've also got articles on construction 
of quads, simple quads, and quad masts. 
This issue will arrive in the midst of the 
spring antenna season and should result in 
many antenna parties aromid the world as 
! i ims decide to improve their signals on both 
( ransmit and receive, 

June is our surplus month. This year, 
we're planning to have plenty of good sur- 
plus articles and, hopefully, many pages of 
surplus ads. If you'd like to write a surplus 
conversion for vis, remember: 1. We only 
want conversions on available gear* 2. We 
don't want rehashes of old articles, 3. Do it 
now* 

A note to surplus dealers: Start prepar- 
ing now for our surplus issue. It's the finest 
opportunity to sell your stock you'll find. If 
youVe got a lot of presently useless stuff, 
put some clever hams to work on uses for 
it; maybe it's even worth an article in 73* 

This year's ARRL National Convention 
will be held in July in Montreal in honor of 
Canada's Centennial and Expo 67, We're 
going to do what we can to honor the ama- 
teurs of Canada by featuring articles for 
and by Canadian hams in our July issue. 
Many of the articles will be technical; others 
will look at the Canadian amateur scene— 
the ridiculously high prices Canadians have 

( Con t in tied on page 116) 



73 MAGAZINE 






so who needs 
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If you're a Heterodyne Harry out for a 'Most 
Unpop Op' award . . . forget the dummy load. 
And win in a walk! But if you realize that a 
consistently clear signal requires constant check- 
ing, tuning and measuring ■ . . you'll check, tune 
and measure into a dummy load and keep the 
heterodynes harmless, We make darn good dummy 
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DUMMY LOAD 

Model 384 Dummy Load handles to 
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Combines with Waters Reflectometer to 
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MANUFACTURING INC. 

WAYLAND, MASSACHUSETTS 



CANADIAN HAMS: You may now order direct 
from M. J. Howard and Co., Ltd., 1300 Carting 
Ave., Ottawa, Ontario. 



See you at the S. S. B. Show, Statler Hilton Hotel, New York, March 21st, 



MARCH 1967 



Rod C. Rigg W6YGZ 
1305 Occidental Ave. 
Stockton, Calif. 95203 



Barry S. Todd K6ZCE 
310 East 10th St. 
Corona, California 91720 



A Transistorized Digital 



Identification Generator 



Here is a description of an exotic, yet very desirable, unit 
that will send your call or other information automatically 
without any motors or other moving parts* It can be built 
for about $15* 



This is a description of a fully automatic, 
solid state, no moving parts, digital device 
for storing and generating upon command, 
a call sign or other message, in the form 
of dc to operate a keying relay for teleg- 
raphy (cw) or a tone to modulate the car- 
rier for mew. It contains all standard, com- 
monly used, digital circuits; the flip-flop, 
multivibrator, and diode fi and" and *W cir- 
cuits* A rough estimate of cost of parts, if 
you buy components at surplus and quantity 
prices as we do, totals $15, 

Just what does it do? Briefly, you push 
the button and it sends your call or any 
other message that you want to "program" 
into it. When it has sent the message once, 
it automatically stops and waits for another 
command, It is not possible to inadvertantly 
'erase" the message for it is <£ built-in" with 
the wiring of the diode memory. Changing 
the message is a simple task requiring only: 

1) the design of the new diode matrix, and 

2) wiring the diodes into their new places, 
A typical call, such as W6YGZ, takes 47 
diodes in the memory, 

"Necessity is the mother of invention" 
and such is the case with the identification 
generator as we will henceforth call it. We 
needed a cheap and reliable unit for iden- 
tifying our transmitters for tests under long 
periods of unattended operation (within 
legal limits of course). We had considered 



I^TTCT 



SOUND 



SYMBOL fQ b a 

Fig. I, Graphical representation of the word "at. 1 



the other methods. A tape recorder uses 
moving parts and the tape wears out rapidly, 
A code wheel or perforated tape unit also 
uses moving parts. All require frequent 
attention to alignment, adjustment, or re- 
placement of worn parts including tape. 
What we needed had to be reliable for long 
periods of time, cheap, compact, and capable 
of changing the call with nominal effort. 

The digital computer approach was fa- 
voreel because of the authors* background 
and familiarity- The unit was designed us- 
ing "digital sequential circuit design tech- 
niques", a specialized branch of digital com- 
puter design, which is a carry-over from 
relay circuits, 

It is assumed that the reader is familiar 
uith the basic digital circuits; AND, OR, 
FLIP-FLOP, MULTIVIBRATOR, INVERT- 
ER. Several references cited in the bibliog- 
raphy treat the subject well. The QST, 
August 1965 article gives a quick review. 

A diode matrix was chosen for the mem- 
ory unit because of the author's immediate 
familiarity with this type of memory. Differ- 
ent types of memory are presently being con- 
templated including a fixed magnetic core 
and a programmable magnetic core type. 

A characteristic of this unit which is com- 
mon to all three types of memory mentionc 
is that the stored message is changeable; 
requiring the replacing of diodes in the diode 
matrix, rerouting sense lines in a fixed mag- 
netic core memory, or simply re-storing a 
new message in the programmable mag- 
netic core type. 

One of the basic questions which arises 
in the initial design is: in what way should 
the message be broken down and stored? 



73 MAGAZINE 




Top view of +he digital identification generator. 

Important criteria in this decision are mem- 
ory size, circuit complexity, and the ability 
to store many types of messages. There are 
three ways in which a message or word can 
be broken down: 

1) By letter. This would require a mem- 
ory capable of remembering any one of 26 



letters, 10 numbers, and certain other char- 
acters, It would not require many memory 
locations. A short message such as a call 
would only contain 5 or 6 letters and num- 
bers, 

2) By character, ue. dot, dash, or blank. 
This would require a memory capable of 
storing one of three possible characters. 
More memory locations would be needed 
for the same message than for method 1) as 
each letter would contain from one to six 
characters (period has 3 dots, 3 dashes). 
The call W6YGZ contains 23 characters in- 
cluding spaces, 

3) By baud. A baud is a telegraphic unit 
of time, a dot is one baud, a dash is three 
bauds and a blank is three bauds (the term 
is more commonly used in teletype). A unit 
of this type need'only .emembefone of two 
characters, presence of a baud or no pres- 
ence. For example, the letter "a" would con- 
sist of a single baud followed by a space 
baud followed by three more bauds for a 
total of five locations. An advantage to this 
system is that only one of two characters 
nerd be ivmembered leading to the binary 




COUNTER 
OUTPUTS 



MATRIX 
OUTPUTS 



SAMPLING SATE 



*A" 



3 BAUD 
MON05TASLE 

MULTIVIBRATOR 





NOT£ 

INV ■ INVERTER 

EF - EMITTER FOLLOWER 



AND 




IDiTl 








< BAUD 
MONOSTABLE 
MULTIVIBRATOR 


*■ 




1 








r 




1 


f 




MV 




INV 






. 




I 





I BAUD /"*" ~~h+—[ AW 

NOSTABLE -*< 3P \ ^ ^ 

H VIBRATOR X^ V^H 



«CALL W PROGRESS 
^OUTPUT 




START INPUT 

Fig. 2. Block diagram of the automatic code generator. 



MARCH 1967 



-12 




INPUT 



DWOCS; AMY SMALL SIGNAL (IN34, ETC) 
TBANSISTORS: £N404, 2N36iB,tTC 



Pig. 3. Typical three stage counter. 



system of one, zero, for the memory. The 
number of locations would be exceedingly 
large. 

Method 2) seemed to be the most prac- 
tical in light of the criteria involved, so it 
was chosen for this unit. A memory capable 
of three characters is only slightly more 
complex than a two character memory 
(method 3). The tremendous saving in num- 
ber of memory locations for a given message 
is the deciding factor. 

Using this method, it is only necessary to 
build a memory to provide signals which 
will, at the proper times, trigger circuits 
generating the dot, dash and blank (no let- 
ters). These circuits are simply monostable 
or one-shot multivibrators with width times 
of one baud (dot), three bauds (dash), and 
three bauds (blank). 

As an example, consider the message 
"at". Tt consists of a dot, a dash, a blank 
for between letters, and a dash, This is 
illustrated graphically in Fig. 1, Using 
the following abbreviations; t = dot, 
a = dash, b — blank, the memory would 
be called upon to provide the following 
signals: t a b a. 

So far so good, But there is one more 
problem; we must provide a short space be- 
tween characters. If this were not done, the 
characters would be run together. An addi- 
tional monostable multivibrator is needed to 
delay the beginning of the next character 
until this space time is over. This time is 
called a "space". It is not to be confused 
with the blank, which is an absence of a 
character denoting the spacing between let- 
ters* The "space" occurs between characters, 



We have established that we need four 
different time segments corresponding to 
the four parts of the telegraphic code: dot, 
dash, blank, and space. Since the length of 
time for the dash is the same as that for 
blank, it is a simple matter to combine them 
into one multivibrator; hence, the dash mul- 
tivibrator doubles as the blank generator. 
We need only insure that there is no out- 
put during the blank time. 

Previously we mentioned memory loca- 
tions. We prefer to call them states. The 
capacity of a system is the amount of infor- 
mation it can store and generate and is de- 
termined by the number of different states 
or combinations that system can have. These 
states are identified by the various values of 
the counter. Thus, the length of message that 
can be stored is dependent on the number 
of counter stages, If the counter contains five 
stages; then, counting in the binary system, 
we can determine 32 unique states, i,e« there 
are 32 possible combinations of counter out- 
puts. Each of these combinations is called a 
state; and each state can be identified with 
one character of the message we have stored, 
32 bits is enough capacity for most amateur 
call signs. 

As mentioned previously, this unit was 
designed using sequential circuit techniques; 
This means that there is no clock to pace 
the system; it goes on its own timing. Each 
circuit triggers the next and so on until it 
decides to stop. It will be best to keep this 
concept in mind when reviewing the opera- 
tion of the svstem. 

Reference to the block diagram, Fig. 2, 
will show the main components of the sys- 



8 



73 MAGAZINE 



tem. They will be discussed in this order; 
counter, diode matrix, character formation 
generators (multivibrators) , space forma- 
tion generator, output circuitry. 

The counter, a five stage binary counting 
chain, determines the particular state of the 
system and hence the next character to be 
generated. It consists of five bistable cir- 
cuits or flip-flops which are connected in 
cascade so as to count input pulses up to 
32 then reset Outputs are taken from each 
flip-flop and fed to the diode matrix. A 
diagram of a typical three stage counter 
with its interconnections is shown in Fig, 3. 

It is in the diode matrix that the message 
is stored, hence it is the heart of the sys- 
tem. The matrix intreprets each state of 
the counter and feeds a signal to one of 
the character formation generators. "Diode 
matrix" is just a fancy term meaning a col- 




Oblique view of the diode matrix that determines 
what characters will be generated. 



A, 
A* 

Ai 
At 




At O 



Aj O 



An O 
As O 



At 




DAN 



At 



(A) BLOCK DIAGRAM 




Ai 




OAK 



(B) SCHEMATIC DIAGRAM 

Fig. 4, The diode matrix in thre* different representations: 
C. Matrix form* 



(C) MATRIX FORM 

A. Block diagram. R, Schematic diagram. 



MARCH 1967 



^^ 



COUNTED STATE NUMBER *- I -l* 

LETTER |— 

CHfiftACTER 
POINT "C" SAMPLING GATE 



m 3 

A 



-U BLANK 



*H T H 



STOP ^ t g DAM ^ BUWK! 



8 



LJ 



E 



A. 






[U 



Jl 



OfT OUTPUT 

POINT V 
OIT MV OUTPUT 
OAH OUTPUT 
POtMT *e* 

OAH MV OUTPUT 



POINT *D" 



SPACE MV OUTPUT 
STOP OUTPUT 
OUTPUT 



J — L 



J — L 



J~L 



i r 



u — u 



n n n n n 



ru — l 



j — i 



Fig. 5. Timing diagram for generating the word "at. 



•i 



lection of "and" and "or" circuits that have 
been arranged in an orderly maimer. 

Obtaining the "equations" for setting up 
the diodes in the matrix is the only com- 
plicated portion of the design of this unit 
It is necessary to determine the arrange- 
ment of diodes such that either output line, 
dot or dash, has the proper signal or ab- 
sence of signal for each individual state of 
the counter. Obviously it is desirous to do 
this with a minimum number of diodes to 
keep the cost, complexity, and size down. 
The actual techniques are a bit beyond the 
scope of this article. However, they may be 
found in several of the references in the 
bibliography. If you are planning on build- 
ing a similar unit, we will design the matrix 
for your particular message for a small cost. 

The diode matrix is simple in appearance 
but complicated to design. A typical block 
diagram is shown in Fig. 4 A, its corre- 
sponding schematic diagram in Fig. 4B, and 
the same circuit in matrix form is shown 
in Fig. 4C. 

Simply stated, the diode matrix consists 
of two level structures of "and' 1 and *W 
circuits which select the proper states of the 
counter and provide outputs during (and 
only during) those states. 

The design procedure involves Karnaugh 
mapping and writing minimal equations. The 
matrix can easily be built from the equa- 
tions. 

We have not set a definite charge for the 



service. The time required to develop the 
equations depends on the nature of the 
message, the amount of "professionalness" 
of the code desired and the degree to which 
the design is minimal (i.e. minimal cost). 
An estimated typical time for a call would 
be two hours. 

We would like to see our device built by 
someone else and would probably charge 
only a nominal fee if the person can show 
a bona fide interest The design fee is to 
discourage non-interested persons from 
wasting our time. 

The character formation generators, as 
stated previously, are monostable multivi- 
brators. These two circuits are triggered by 
the outputs of the diode matrix. A dot out- 
put triggers the one baud length MV (multi- 
vibrator), a dash triggers the three baud 
MV which together with the dash output in 
an AND circuit causes an output. The blank 
also triggers the three baud MV but there 
is no output. 

When either of the character multivibra- 
tors has completed its function, the space 
multivibrator is triggered. The space MV, 
sends a pulse to the counter when it is first 
triggered, This moves the counter up one 
state. When the space MV is completed, a 
pulse is sent to the sampling gates which 
in turn gates a pulse to either formation MV 
depending on the output of the diode ma- 
trix. And the cycle repeats itself. 

The output circuitry simply combines the 
outputs of the two character formation gen- 
erators and gates on and off a tone gener- 
ator for mew or operates a relay for cw. 
There is provision for inhibiting an output 
during a blank. 

One last thing which we need to mention 
is a method of stopping the generator after 
it has sent the message once. The method 
is simple. A third output from the diode 
matrix, called a stop, is provided. The stop 
output occurs after the counter has com- 
pleted 32 counts. When the counter reaches 
that state the stop output gates off the space 
MV input pulses from the formation MVs. 
This interrupts the sequence and the unit 
remains dormant until restarted. To start 
again, a pulse is fed to the space MV. The 
next state does not have a stop signal so 
the space MV input pulses are again gated 
on and the circuit continues thru its se- 
quence. 

The entire unit timing diagram is shown 
in Fig. 5. A careful study will lead to a 



in 



73 MAGAZINE 



r» 



HWUUH 






I 3 



a 



CO 



2 3 











o a 

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better understanding of the operation of the 
generator. The example shown has been se- 
lected to show most of the details of opera- 
tion. The following events happen in se- 



quence: The counter is initially in the stop 
state (no. 1). A start pulse fed to the space 
MV input turns it on incrementing the 
counter to the next state (no, 2). The diode 



-10.3 




SUPPLY 



-0,5 




0-I2 



tOPtNJ 



Fig. 7. Circuits for measuring transistor parameters. 
See the text for a description of how to use these 
circuits. 

matrix interprets this state as a dot, When 
the space MV returns to its quiescent state, 
the matrix output is sampled and the dot 
MV is triggered generating an output, When 
the dot MV is up, the space MV is again 
triggered incrementing the counter to the 
next state. The cycle continues until the 
stop state again occurs. 

Going from block diagrams to actual cir- 
cuitry; logical levels of "one** are —12 
volts and those of "zero" are zero volts. The 
schematic of our working model is shown 
in Fig* 6, An understanding of the operation 
of each of the individual circuits can be 
gained by reading one of the many texts 
and articles on the subject of digital cir- 
cuits. Some of them are included in the 
bibliography. 

It must be kept in mind that we are not 
dealing with ideal components when build- 
ing digital circuits: diodes have finite for- 
ward voltage drop, finite back resistance, 
transistors do not have infinite gain nor zero 
"on" voltage drop. The voltages at each of 
the logic points are not exactly zero and 
^12. They are close enough that the circuits 
still work with good reliability. Keeping the 
voltages and circuit operation as near ideal 
as possible is the main criteria in selecting 
the resistance values for each circuit Ca- 
pacitor values determine the timing details. 
An oscilloscope is handy for debugging the 
circuits for their final design but is not ab- 
solutely necessary. 

Typical voltages are not shown on the 
schematic because each point has a voltage 
which is continually changing from one val- 
ue to another* Voltage waveforms at the 
more important points are shown in the 
timing diagram. 

Obtaining parts at a minimum cost has 
always been a concern for the amateur, The 
circuit design of this unit was done with 
low cost in mind* The surplus market is a 
good source of resistors, capacitors, and 



diodes at prices well below the industrial 
prices you pay for new material, 

It is also true that transistors are avail- 
able at quite low prices but, it has been our 
experience that the industrial units are more 
economical and desirable. Most surplus or 
used transistors are not adequate for digital 
service and out of a bargain bag of surplus 
transistors many will not work reliably. 

With the introduction of the cheap silicon 
transistors, it is more economical to consider 
the industrial units. For example, the trans- 
istor used in the identification generator, 
Fairchild 2N3638, is 31c in quantity. This 
fact together with the assurance of known 
characteristics and uniformity of quality 
makes the choice an easy one. Paul Franson 
discusses the 2N3638 in his column; 73 
Magazine, June 1965, page 88. 

Surplus transistors can be used but should 
be tested first, A few simple tests will de- 
termine if a transistor is suitable for use in 
digital circuits: 1) The dc beta should be 
greater than 30, DC beta, hm. is deter- 
mined by measuring what base current is 
needed to produce 5 mA of collector cur- 
rent with the collector-emitter voltage 0,5 
volts, DC beta is the ratio of collector cur- 
rent (5 mA) to base current, 2) The leak- 
age current should not exceed 200 micro- 
amps. Leakage current, Leo, is the collector 
current with the collector-emitter voltage 12 
volts and the base open. Circuits for mea- 
suring both these parameters are shown in 
Fig, 7. These are relatively simple tests but 
they tell quite a bit in comparing transistors. 
Units that meet these two tests will general- 
ly work satisfactory in digital circuits. 

Other types of transistors will work 
equally well 2N414, 2N404, 2N1305, are 
just a few. Practically any transistor will 
work if it meets the above tests, NPN units 
can also be used if battery and diode polar- 
ities are reversed* 

Many variations on this idea are possible. 
Amateurs in the RTTV field might like to 
consider this unit for solving the problem 
of dual identification. As the FCC rules 
stand, onlv the identification of the trans- 
mitting station is required to be in cw. The 
requirement can be fully met with this gen- 
erator and a ten minute timer to trigger it. 

The ragchi r will find a unit such as 
this an extension of his "ten minute re- 
minder*' (it is mi sled that the reader con- 
sult the rules and regulations part 97,87 
before making final plans). 



12 



73 MAGAZINE 



For the amateur who likes it deluxe, this 
unit can be the basis for a semi-automated 
cw station. 

With a magnetic core memory many vari- 
ations of the basic design are possible; for 
example, several messages can be stored in 
the memory and called for individually to 
satisfy various situations. For instance, the 
following messages could be contained in 
memory: CQ CQ CQ DE W6YGZ, town, 
handle, TESTING, 73, and so on. Each could 
be selected to fit the need. The possibilities 
are limitless. 

For the contest minded (or the novice) a 
unit with the message: "CQ SS CQ SS CQ 
SS DE W6YGZ" might be the answer. The 
message need be stored only once but could 
be called out three times in a row if a 
simple three counter is used. 

Thanks go to L S. Reed of the University 
of Southern California for the idea and 
background. Photo credit to Rod C Rigg- 



Bartee, Tjebow, and Reed, Theory and Design 
off Digital Machines, McGraw-Hill, 1962. A more 
sophisticated approach to the design of digital 
systems, covers sequential circuits. 

Burrougl Corporation, Digital Computer 
Principle*, McGraw-Hill, 1962. A nonmathe- 
matical explanation of dig'itnl romputers, their 
operations, and the components that make 
them work. 

Caldwell, Samuel H, ( *\vHHtiii^ Circuit* and 
Logical DeHigrn, Wiley, 1962, A little of every- 
thing* in the design of digital relay systems. 

Granberg, TL U OH2ZE, "A Push-Button 
Keyer", CQ Magnxinis 20:9 Sept, 1964, Page 28* 

Uses magnetic core shift register, 

Horowitz, Paul, W2QYM, 'Perfect Code at 
Tour Fingertips'. QST 49:9 August 1965, Page 
11* Uses diode matrix and magnetic core shift 
register. Typewriter keyei\ Explains digital 
circuits. 

Hurley, Richard B., Trims!** lur Logir Circuits, 
Wiley, 1961. A College level text explaining 
digital mathematics, design and circuits detail. 

Ketchum and Alvarez, Pulae and Swift-Inn^ 
Circuits, McGraw-Hill, 1965, A junior college 
treatment* 

"A Semi -Automatic Keyer'% an article in 
I [rvtroiijis Experimenter. Some issue In 1064 
or early 1065. Shows how to build a type- 
writer-like code generator using relays, 




Bottom view of the automatic Identification generator described in the text. The diode matrix is in 
the lower right corner. 



MARCH 1967 



13 






Robert Crotinger K6YKH 
4619 Brighton Avenue 
San Diego, California 



Sideband Proof of Performance 



Have you ever checked your gear to see what it can do? It's interesting, 
and can often lead to improved results* 



Broadcast stations are very familiar with 
the term Proof-of-Performance". It desig- 
nates the series of specified measurements 
that must be made, set down on paper, and 
filed with the FCC before a station license 
w ill be issued. Though no such requirement 
is made for amateur stations, compiling a 
similar set of data will probably reveal 
many things about your installation which 
are worthy of correction. 

The idea of a graphical analysis of the 
performance of my equipment setup came 
about when I purchased a new exciter cap- 
able of overdriving my linear. It seemed 
desirable to construct a pad of approxi- 
mately three decibels attenuation to correct 





1.0 


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3 4 6 6 7 

RELATIVE POWER OUTPUT 



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*o 



2».4 MHz 



,■ 



TR-5 
EXCITER 



H3dB PAD fcSB-201 I ^ 

52 jl ~^ LINEAR 



VSWR / PWR 
METER 




EQUIPMENT 
SETTjNGf 



Tfl-3 

PLATE TUNING 
PLATE LOADING 

XMTfl SAIN 
RF TUNE 
IpMAX 



4.2 
5.5 

.420A 



UNEAR 

TUNING 

LOADING 

V5WR 

P-2 SENSITIVITY 

!p MAX 



\A 

2& 

17 

2,0 

620A 



Fig* I. Plate current of the TR-3 and linear versus 
relative power output. 



the situation. However, to determine the 
precise benefits, or obtain a quantitative 
conception of these benefits required some 
sort of testing. Graphical plotting of the 
results was the logical approach* 

A graph in two-dimensional form shows 
the variation of a dependent, plotted verti- 
cally, when an independent variable, plotted 
horizontally, is caused to change through a 
predetermined series of values. The plotting 
is done after a series of tests have been made 
at a relatively large number of values of 
the independent variable and the values of 
both variables tabulated. 

Carrying out a good test requires: 1. a 
decision as to what items are to be meas- 
ured, 2, finding an independent (control- 
lable) variable which will put the depend- 
ent variable to the test as much as possible, 
3. tabulating the results as accurately as 
possible while the test is being made, 4. put- 
ting the results in a form which will best 
show the variation taking place, and 5, anal- 
ysis of the results. 

Amateur measurements usually fall into 
the "comparative" class, as access to precise 
standards is usually impossible and the re- 
sults are relative to a given set of conditions. 
Therefore, it is desirable to plot more than 
one measureable dependent variable if pos- 
sible in order that accuracy will not depend 
on any one measuring instrument. Also, the 
results of one plotted curve can support the 
results of another, making the analysis more 
positive. 

The results of the first attempt at meas- 
urement are shown in Fig, 1 and represent 



Bob is a technical director at KFMB-AM- 
TV. He used to be WOGUY and W8DDT. 



14 



73 MAGAZINE 



s 



n 



*40 = 



LINEARITY 
RESPONSE 




AUDIO 




LINEAR 
G58-20I 



VSWR 

METER 

KNIGHT 

P-2 




NOTES 



VSWR {EXCTTER -LINEAR)- 1,3 t | 
TUNING A SETTINGS AS PER FtG. f 
VARIABLE = AUDIO INPUT LEVEL 
AUDIO FREO - 1000 Hi 



Pig. 2, Linearity response, 

a test which could be made quickly and 
easily by virtuaDy any station with only a 
VSWR meter with a relative power scale. 
Carrier is inserted and the level increased 
as readings of relative power output are 
taken, along with exciter plate current and 
linear plate current- This test is informa- 
tive, but the fact is that the independent 
variable is not measureable and the results 
do not show the most important variation, 
that of power output with input audio level. 
However it is a reasonably good indication 
of the linearity of the two stages with drive. 
An important conclusion from this graph 
was the fact that the driver (TR-3) reached 
450 mA, its maximum output where flat- 
topping begins, at the same time that the 
linear had only reached slightly over 600 
mA. The linear was capable of being driven 
to slightly over 700 mA before flat-topping; 
therefore it was obvious that on this band 
(15 meters) the 3 dB pad presented more 
loss than desirable. The ultimate conditions 
was that both exciter and linear flat-top at 
the same point. 

A more valuable test was effected when 
an audio oscillator was used with the out- 
put attenuated to mike level and fed into 
the microphone input, as shown in Fig, 2, 
While a commercial unit was used here with 



10 

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8 

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6 

5 

4 

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2 

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.30 

45 

JO 

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INPUT TONE FREQUENCY 



2-lkHt 3kHz 



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-l 



1 



AUDIO 

05C 

HP-205AG 




EXCITER 

DRAKE 

TR-3 




LINEAR 
638-201 




VSWR 

METER 

KNIGHT 

P-2 




NOTES 



't/SWR = 1.20 - I 

TUNING A SETTINGS AS PER FIG. I 

VARIABLE * AUDIO DSC FR£0 



Fig, 3. Overall audio response, 

a step attenuator and db level variation 
read accurately, it is equally as valid to use 
any audio oscillator in conjunction with a 
resistor-potentiometer voltage divider to re- 
duce the level and take readings of audio 
level with a VTVM at the audio oscillator. 
In many cases, a decibel plot will improve 
the appearance of a curve over a voltage 
plot and converting to decibels is not always 
necessary or even desirable. Use the method 
of plotting which will emphasize the defi- 
ciencies, they are what we are looking for. 

In any case, the second set of curves 
shows that the exciter has become delight- 
fully linear, however on this band (40 me- 
ters) it reaches 300 mA plate current when 
the linear begins to level off* In this case, 
it would be better to have slightly more 
padding in order to make the exciter ALC 
work, thereby raising the average level of rf 
a few decibels. Another revelation from the 
curve is the non-linearity in the low plate 
current region in the linear, a condition 
which is supported by the relative forward 
power curve in this region. While non-lin- 
earity' at this power level is not as serious as 
at maximum output, it is worthy of some 
attention in the future. 

While the audio oscillator was available 
it seemed worthwhile to make an overall 
frequency response run, the result of which 



MARCH 1967 



15 




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These advantages are the result 
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is shown in Fig. 3. In making this run the 
input audio at 100 Hz was increased until 
the linear plate current had ceased rising. 
It would have been preferable, for observa- 
tion of the "top" of the response curve, if 
a slightly lower level had been used since 
it appears that the leveling-off of the ampli- 
fier output has produced an apparent flat- 
ness across^the response that is "too good 
to be true". However, the exciter exhibits 
this same condition and perhaps the actual 
response over this range is not considerably 
different from that indicated. The more im- 
portant aspect of the curve is the steepness 
of the sides. It shows very definitely the 
fact that the exciter used the steepest side 
of the filter response on the side toward the 
carrier. This results in the response encom- 
passing a greater area of lows. Since the 
apparent "volume" of the voice is carried 
by the low frequencies, this may account 
for the seemingly greater "punch" provided 
by one transmitter over another of equal 
power. 

The small step is the response of the 
exciter at 2.7 kHz is interesting but prob- 
ably rather inconsequential. 

I have made no attempt here to "doctor 
up" any of the results nor to minimize the 
shortcomings of the test procedures. These 
are the purpose of testing and it is readily 
seen how the test procedures can be im- 
proved and why. It is also appropriate to 
remark here that when testing anything it 
is desirable to write down everything pos- 
sible pertaining to the conditions of the test, 
whether it seems pertinent at the time or 
not The author keeps index cards in the 
optimum dial settings and current readings 
on each band. Also, it is naturally best that 
tests be made under the same conditions 
that the equipment is used, and this means 
into the antenna. This dictates the making 
of overall tests at a time when the band 
is dead. 

The advent of commercial transmitter 
manufacture has taken some of the adven- 
ture out of ham radio for some of us who 
used to build such equipment. However, the 
author is willing to concede that "they can 
build a better one than he can, and it has 
better trade-in value". This does not mean 
that we must be unaware of how it operates 
or what it is doing, and it is hoped that 
this article may produce some incentive in 
that direction. . . . K6YKH 



16 



73 MAGAZINE 



Excellent performance 




AMATEUR NET 



Matching Speaker 

Model 2-CS 

$19,95 Amateur Net 



• Covers ham bands 80, 40 P 20, 15 meters com- 
pletely and 28,5 to 29.0 mHz of 10 meters with 
crystals furnished 

• Or tunes any 500 kHz range between 3.0 and 
30 mHz with an accessory crystal. 

• Three Bandwidths of selectivity (equivalent to 
3 fitters) are furnished: ,4 kHz, 2.4 kHz and 
4.8 kHz. 

• Solid State Audio with 1,8 watts output. 

• Solid State AVC with fast attack and slow re- 
lease for SSB or fast release for high break- 
in CW\ Also AVC may be switched off. 

• Receives SSB f AM, CW, and RTTV with full 
RF gain, complete AVC action and accurate 
S-meter indication. 

• Product Detector for SSB/CW— <liode detec- 
tor for AM, 

• Excellent overload and cross modulation 
characteristics; insensitive to operation of 
nearby transmitters. 



m 




S39.95 Net 



2-CQ SPEAKER/ 

©-MULTIPLIER & 
NOTCH FILTER: 

Plugs into a sock- 
et on the 2-C to 
provide i n- 
creased selectiv- 
ity and notching 
out of interfering 
hetrodynes and other interfering signals. Nee* 
essary controls are mounted on the 2-CQ. 

2-NB NOISE BLANKER: Solid state circuitry is 
used to provide true notse blanking by quieting 
the receiver during the interval of the noise 
pulse. 

2-CS MATCHING SPEAKER 

2-AC CRYSTAL CALIBRATOR; 100 kHz crystal 
oscillator corresponding to the numbered dial 
divisions on the Main Tuning Dial 



SPECIFICATIONS 

FREQUENCY COVERAGE: 3,5 lo 4.0 mHz. 7.0 to 7.5 mHz. 14.0 to 14,5 mH*. 21,0 to 21.5 
mHz and 28 5 to 29.0 mHz with crystals supplied. Accessory crystals provide 500 kHz 
incremental coverage from 3.0 to 30 mHz 

SELECTIVITY: Selectable Passband FHter provides: 
.4 kHz at 6 DB down and 2 7 kHz at 60 DB down. 
2.4 kHz at 6 OB down and 9 kHz at 60 DB down. 
4.8 kHz at 6 DB down and 16.8 kHz at 60 DB down, 

DIAL CALIBRATION: Main dial calibrated to 500 kHz in 10 kHz divisions. Vernier 
dial calibrated in approximately 1 kHz divisions. Main dial and Vernier adjustable tor 
calibration, 

STABILITY: Less than 100 Hz after warm up. Less than 100 Hz for 10% line voltage 
change. 

MODES OF OPERATION: USB, LSB, CW, AM, RTTY. 

SENSITJVITY: Less than .5 uv for 10 DB signal plus noise to noise on all amateur 
bands. 

AVC: Amplified delayed AVC having slow (75 sec, J or fast (.025 sec.) discharge and 
less than 100 microsecond charge AVC can be switched off. Less than 6 DB change 
for 100 DB RF input change. 

AUDIO OUTPUT: 18 waits with less than 5% distortion and .75 watts at AVC threshold 

AUDIO OUTPUT IMPEDANCE: 4 ohms. 

ANTENNA INPUT; Nominal 52 ohms. 

SPURIOUS RESPONSES: Image rejection greater than 60 DB. IF rejection greater 
than 60 DB on amateur bands. Internal spurious signals within amateur bands less 
than the equivalent of a 1 uv Signal on the antenna. 

CONTROLS AND JACKS: 

Front: Main Tuning, Function switch- Band switch, Preselector RF Gain. Mode, 
Selectivity switch, AVC, and S-Meter, 

Rear: Antenna jack, S-Meter Zero, Mute Jack, Sidetone Jack, and Speaker Jack. 

Side: Auxiliary crystal socket, auxiHary crystal — Normal switch Phones. 

Top Chassis: 2-CO socket, 2-AC socket and Noise Blanker socket 
POWER CONSUMPTION: 30 watts, 120 VAC. 50/60 kHz, 
DIMENSIONS: 11 V *^ *Hi* n, 9 h - 9%" deep, weight \ZY 2 lbs. 



2-C BLOCK DIAGRAM 



. <i 



«' / j 8*1 




1*1* 



See your distributor or write for free Brochure 



H. L. DRAKE COMPANY • miamisburg, ohio 45342 



Jotin Schukz WIDCG 
40 Rossi© St, 
Mystic, Connecticut 



A Non-Tiring CW Monitor 



For anyone who enjoys long periods of 
CW operation, a good keying monitor is a 
necessity. Unfortunately, most simple moni- 
tors which produce a single tone get awfully 
hard on the ears after a while and many 
experienced CW operators still resort to 
using their receivers as a monitor. They do 
this because of the pleasing tonal quality 
of the multi-frequency signal and because 
one can "play" with the receiver taming to 
vary the tone* 

It would, of course, be better to have a 
keying monitor that sounds like the receiver 
signal and to leave the receiver tuning alone. 
One can come pretty close to this ideal by 
use of a dual-tone monitor. Some years ago, 
I built such a monitor but forgot about it 
when my interest turned to SSB, Now, with 
a returning interest to CW, I decided to 
update the monitor using transistors. 

The circuit for the monitor is shown in 
Fig, 1. The circuit is simply two variable 




VOLUME 
It 




KEY 



ALMOST ANY 
PNP AUDIO 
TRANSISTOR 



GRID-SLOCK KEYED TRANSMITTERS 




MODIFICATION FOR 
CATHODE-KEYED TRANSMITTERS 



Fig. I* Two-tone CW monitor designed to over- 
come trie monotony of a single sine wave output 
monitor. No parts are critical; al! are discussed in 
♦he tert. 



tone oscillators with their outputs con- 
nected in series to the monitor loudspeaker. 
The diodes Dl and D2 protect the monitor 
from the voltage across the transmitter key 
terminals. These diodes and the battery 
connection must be slightly changed as shown 
for use with a cathode-keyed transmitter. 

I used a Telefunken transistor but prac- 
tically any low-level audio transistor with a 
B of 50 or more will work* Some examples: 
2N138, 181, 186, 217, 223, 249, 270, etc. 
The diodes Dl and D2 may be any type- 
normal power supply silicon diode units work 
fine— having a PIV greater than the voltage 
measured across the open key terminals. A 
battery supply is shown, however, any op- 
erating voltage between 6 and 15 volts is 
satisfactory and this voltage can usually be 
"borrowed" from some well filtered point 
in a transmitter or receiver. If a battery 
supply is used, the resistance across the 
open transmitter key terminals shonld be 
checked. With some transmitters this re- 
sistance is only several thousand ohms and 
an on-off switch must be used in the monitor 
to prevent a continuous battery drain. 

I built the monitor in a small Minibox 
measuring 3% x 2& x 2% inches so it could 
be used as a separate unit for portable op- 
eration or as a CPO, It could just as easily 
be constructed on bakelite circuit board and 
mounted inside a transmitter. The exact 
frequency range of the oscillators will de- 
pend on the manufacture of the components 
used but should be about 700 to 2000 Hz, 
The combinations of tones from two oscilla- 
tors with this range should satisfy anyone's 
desire to change the monitor tonal quality. 

Although conceived only as a keying moni- 
tor, some other uses for such an oscillator 
suggest themselves: a two-tone test oscilla- 
tor for SSB measurements and as a CW 
generator/kewer for an SSB transceiver with- 
out CW provisions by feeding the output of 
only one tone oscillator to the microphone 
input of the transceiver. For these applica- 
tions, however, it is essential that the output 
of each oscillator be checked on an oscillo- 
scope to be sure that it is a good sine wave 
at the tone control setting (s) used. 

WIDCG 



* > 



18 



73 MAGAZINE 






K 


















Amateur Mirfiiie Antenna IOOO 



DX'ers . . . For a commanding mobile signal, Mosley an- 
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A reduction of corona effect due to a Mosley innovated Corona 
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Box I39C. Route #2 
Amherst, Virginia 



Seven Elements on Twenty 



Here's a high gain, low cost beam that will really help you get out on 
twenty meters. Why not join the big boys? 



In antenna design, as in boxing, it is true 
to say "A good big un can beat a good little 
iin". Tuning across the favorite DX band, 
14MHz, proves this axiom again and again 
as we hear the choice DX returning to the 
fellows with the big beams mounted on high 
towers. However, the bigger they are the 
more they cost, and even though kind neigh- 
bors may not object, the financial strain 
does not allow the average ham the luxury 






Fig. I. Details of three parts of the antenna. From 
tht top: Addition of extensions to the ends of 
the reflector for tuning. Element attachment to the 
boom. Attachment of the boom to the mast. 



of a big antenna* The following description 
of my antenna is to give some idea of a low 
cost approach to a large Yagi design on 14 
MHz. 

The first consideration is the wind load 
on a large structure— how strong must the 
beam be to withstand winds to 60 mph? 
Two approaches were considered. First, a 
rigid boom using a triangular aluminum 
tower. Second, a tubular boom with a degree 
of flexibility to "ride" wind gusts. It was 
decided to follow the second approach using 
relatively small diameter tubing, with braces 
to take the vertical load of the elements- 
Sixty feet of boom was selected as a good 
compromise between cost and performance. 
For the operator who wishes wide band op- 
eration between CW and phone this boom 
length will allow l A wave spacing with five 
elements. For the phone or the CW enthu- 
siast more elements can be added to give a 
narrower beam width for better QRM re- 
jection on receive, and a little more gain 
on transmit. As my antenna was to be used 
mainly on phone SSB, a center frequency of 
14.270 MHz was chosen with seven elements 
at ,15 wave-length, approximately 10 feet 

spacing. 

A visit to the local electrical store pro- 
duced 2 inch LD. conduit with .125 inch 
wall Two 10 feet lengths were purchased, 
and a piece cut off each, one foot long, to be 
used as a coupling between boom sections 
which are 2 inches 0,R Four lengths of al- 
loy tubing were purchased 2 inch CXD., two 
at 1 2 feet, two at 9 feet, wall thickness .065 
inches. 

Now to assemble the boom on the ground, 
A screw coupling is supplied with the con* 
duit, so the two 9 feet lengths are coupled 
together, and two 3 inch, M inch D, bolts 

fitted through the coupling for added me- 



20 



73 MAGAZINE 




Fig. 2. WA4WWM's seven element twenty-meter beam. Dimensions are given In the text. 



chanical security. At either end of the con- 
duit a 3 inch cut is made with a hack saw. 
Now, a 12 foot length of 2 inch CD. alloy 
tubing is inserted in either end of the con- 
duit and a strong joint assured by a 2J£ 
inch muffler clamp. These muffler clamps 
are very strong and cost less than 25 cents 
each. Six at 2 inch and ten at 2& inch were 
bought from the local auto accessory store. 
The remaining two 9 feet lengths are joined 
to both ends of the construction using the 
two one foot sections of conduit which have 
been previously slotted with the hack saw 
for 3 inches either side. This coupling is 
now made tight with two 2K inch muffler 
clamps. We now have a 60 foot boom lying 
on the ground looking extremely flimsy 
especially w r hen picked up at the center! 

Each element is made from alloy tubing. 
The center portion is the standard 12 foot 
of 1 inch O.D., .058 inch wall, with another 
12 foot of % inch CD. cut into equal parts, 
inserted at either end, and still another 12 
loot length of % inch O.D, tubing cut in half 
and inserted into the % inch sections. Now, 
the beam element is 34 feet long, allowing 6 
inches insertion for each joint. Holes were 
drilled and self -tap screws used to ensure a 
rigid mechanical coupling. The 34 feet 
length is sufficient to allow trimming of the 
driven element and directors, but extra 
length is required for the reflector, approxi- 



mately 9 inches at either end. Two strips of 
aluminum 1 inch x 12 inches were bent to 
make % inch angle and fixed to either end of 
the reflector with a hose clamp bought from 
the auto store. This makes an easily adjust- 
able tuning device. 

Various methods of feeding the driven 
element can he used, but, as K200 UIIF 
twin line was available it was decided to try 
a folded dipole. Aluminum clothes line wire 
was spaced 4 inches from the driven element 
and gave a 200 ohm match to the line, A 
length of 150 feet of line is used at my 
location, terminating in a % wave coax 
balun to give 50 ohms to the transmitter. 
The length of the driven element is obtained 
from the antenna handbook as 465 /F in feet 
when F is in megahertz. Director #1 was 
found optimum at 445/F, #2, 3, 4, and 5 
progressively shorter to make #5 a 430 /F, 
The reflector should be about 490 /F but it 
is highly recommended that this element be 
tuned for best front to back ratio, 

The elements are now attached to the 
boom by a 12 inch length of IS inch alloy 
angle fixed to the center of the element with 
two l/a inch M inch D, bolts, then the 
angle drilled to take a 2 inch or 2 J* inch 
muffler clamp to suit the boom, the three 
inner elements with 2Ji inch clamps, the four 
outer with 2 inch clamps, 

The element positions should now be 



MARCH 1967 



21 



16th ANNUAL DAYTON HAMVENTION 

Davten Amateur Radio Association 



• Technical Sessions 

• Exhibits 
■ Awards 



• Women's Activities 

• Hidden Transmitter Hunt 

• Flea Market 



Forums 



ARRV, DX, MARS ■ ■ • Technical Sessions * VHF, 5SB, RTTY, Antennas 

SATURDAY, APRIL 15, 1967 

WAMPLERS BALLARENA, DAYTON, OHIO 

FOR INFORMATION, MAP, ACCOMODATIONS, WRITE: 
DAYTON HAMVENTION, DEPARTMENT M, BOX 44, DAYTON, OHIO 45401 



marked, then the whole antenna disassem- 
bled, 1 use a telescoping tower with 20 foot 
sections, so winding this down gave a rela- 
tively convenient height to reassemble the 
antenna, using a 20 foot ladder to work 
at the outer elements* 

The center part of the boom is now 
mounted to the mast, which is rotated by a 
rotor 3 feet down inside the tower. The 
mast is 10 feet long so 7 feet remains 
above the tower. The boom is mounted to 
the mast, again with muffler clamps on a 
Ji inch steel plate 18 inches by 12 inches, 
A % inch hole is drilled through the mast 
and plate and a bolt used here for added 
strength. Two 12 feet lengths of % inch 
tubing are now used to support the ends 
of the inner 18 feet from the top of the mast, 
again using muffler clamps. Next, the two 
12 feet lengths of 2 inch tubing are assem- 
bled to the conduit as before. The ends of 
these are now supported by cable from the 
top of the mast, A 2 foot cross bar of 1% 
inch alloy angle was mounted with a muffler 
clamp and the ends drilled to take the two 
cable's from the mast to either end. Two 




A shot of the beam witk a small quad over if 



turnbuckles at the mast take up the droop 
in the boom at this stage. The cross bars 
give some added strength against lateral 
forces. Now the remaining two boom sec- 
tions are coupled to the structure. We now 
have the boom ready to receive the elements. 
Assemble the outer elements first, keeping 
the array balanced, and there is— a seven 
element beam on a 60 foot boom. 

Some remarks on tuning are appropriate. 
The director lengths quoted are close to the 
optimum but some trimming of the driven 
clement may be necessary to ensure 200 
ohms. It is best to measure this with an an- 
tennascope and a 4:1 bolun to read 50 
ohms. This is a balanced system, hence the 
balim. The reflector can be adjusted with 
ihe aid of a small oscillator located a few 
hundred yards away, or by getting a local 
ham a few miles away to give S-meter read- 
ings. The antenna handbooks will supply 
details, 

Finally, a beam of this size helps tre- 
mendously in reception, 
bandwidth is 45 degrees, 
is about 12 db, but signal reports would 
suggest that this figure is low, especially 
when optimum conditions suit the vertical 
angle of radiation. It is highly recommended 
that a height of at least 70 feet should be 
used with any beam antenna, especially after 
the expenditure of time and energy on a 
large array. 

The antenna described has been in use 
for a year and has withstood winds of 60 
mph with no sign of damage. The cost is 
much lower than the commercial versions 
available. Some of the ideas in this article 
mav also be of some use in the construction 

m 

of smaller Yagis at a relatively low cost 
factor. 

. . . WA4WWM 



as the half-power 
The gain in theory 



22 



73 MAGAZINE 



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H 



Climbing the Novice Ladder 

Part IV: The code is almost conquered. 



Howard S. Pyle W70E 
3434 74fti St*, SE 
Mercer Island. Washing* 



on 



On a Saturday morning just two weeks 
after their last visit to FN's shack, Judy 
and Joe wheeled into the yard and were 
surprised to find Larry leaning against the 
basement door jamb, "Hi, Larry", said Joe, 
"what you doin' out here . • * goin to sit 
in on a code class with us?" 

That's exactly what I am goin to do 
Joe . . . hello Judy; FN phoned me right 
after you'd contacted me to be Judy's ex- 
aminer and suggested that I drop out this 
morning for an informal session with you 
kids . . . here I am!" 

Just then FN appeared, greeted Judy and 
Joe cordially and explained, "I asked Larry 
to come out this morning and we'd put you 
through a little preliminary examination- 
Nothing official about it of course; just a 
run-down to get a double check on your 
progress. So, if you're all set, let's go in- 
side, set up the CPO and see how your code 
looks, You bring your headphones this time, 
Joer 

"Sure thing" Joe replied, "right here" 
and he opened the carrier pouch on his 
Honda and pulled them out along with the 
license manual. Judy produced the ABCs 
book which she had picked up and the four 
of them settled themselves in FN's shop. 

"Larry, put on the phones and take a 




Joe chose to use his SWL receiver — a military 
surplus BC-312-N — for his novice operation. 



listen to Judy's sending; I'll work Joe over 
when you're through. Let her send simple 
English with a few figures and punctuation 
, , . here, you can take a few lines from 
one of these books" and so saying FN 
handed Larrv the two little manuals. 

Picking a short paragraph in Judy's ABC 
book, Larry donned the headphones and said, 
"OK Judy; start right here and send me 
the first three lines in this paragraph." 

FN and Joe remained quiet while Larry 
copied Judy's sending. When she had com- 
pleted her stint, FN took the phones from 
Larry and said, "All right Joe, you send 
these three sentences from the license man- 
ual to me while Larry checks Judy's copy", 

When Joe finished, Larry looked up say- 
ing, "Well, Judy did right well , . , just one 
mistake girl . . . you sent an f N* where it 
should have been an *A* 

"I knew it" Judy exclaimed, "the minute 
I did it but Cramps had told me not to go 
hack and correct a mistake like that in an 
examination but to just keep going, so I 
did", 

"Right, Judy", Larry returned, "you'd 
correct it if you were actually communicat- 
ing with another station but in an exam 
you'd just foul yourself up. Incidentally, 
both FN and I are checking the time it takes 
you to send the copy we give you: we can 
then figure your transmitting speed by 
counting the characters. You were doing 
very close to six words a minute Judy; so 
close we won't split hairs". 

By then FN had counted the characters 
in Joe's copy, clucked his stop-watch and 
announced, "By golly, you kids are running 
practically neck and neck! Joe hit it right 
on the button at six wpm and also made 
but one error , . . the old 'X* for a *Y* again 
Joe; give those !< tiers a lot more play next 
time you practice. Looks like both of you 
made sufficient solid copy a couple of times 
to have put you through the formal exam 
but as far as I'm concerned, Fd like to see 



24 



73 MAGAZINE 






you both up to 7 or even 8 words a minute 
both sending and receiving solid copy before 
we call the torn formallv: what vou think 
Larry?" 

"By all means, Larry came back, "if you 
kids can reach 7 or 8, you'll go through 5 
like nothing; give yourselves those extra 
few words for a bit of leeway*. 

FN then commented, '*You should be able 
to do that in the next couple of weeks if 
you keep up your present pace . , . just 
keep plugging. Let's see now what you can 
do with receiving" and both FN and 
Larry passed the phones to Judy and Joe. 

Larry and FN again alternated between 
sending and checking copy, Again the two 
youngsters were very close; Judy had a 
slight edge and Larry gave her 5.5 wpm 
whereas FN checked Joe out at exactly 5 # 
Judy generously reminded them that she 
had a bit more time to practice whereas 
Joe had his paper route obligation every 
evening. However, both FN and Larry ex- 
pressed satisfaction and both were confident 
that in another two weeks, 7 or 8 words 
a minute could roll out from under both 
their fists and pencils. It was therefore mu- 
tually agreed that if their knowledge of the 
written portion of the examination proved 
equally satisfactory, Larry and FN would 
administer the formal code examination at 
the next session, two weeks hence. The writ- 
ten portion would necessarily have to await 
completion of the formal code test and sub- 
sequent receipt of the other papers by FN 
and Larry, In the meantime, both Joe and 
Judy, independently, were to write to the 
Federal Communications Commission at Get- 
tysburg, Pa. and request application forms 
for amateur radio licenses. They were how- 
ever, not to complete and return them but 
were to turn them over to their examiners 
at the time of the code test. 

The code tests for this session having been 
completed, FN suggested, "Suppose we take 
up the written portion and see what you 
know about that in a verbal test; you been 
studying your books?" 

"Sure* Cramps", replied Judy, "I've been 
getting in some time every afternoon and 
fve been reading myself to sleep at night 
with one or the other of them . , . Joe and 
I have been swapping them between us, 
Kinda rough going in spots but Joe's been 
able to straighten me out on some of the 
puzzlers so I figure Tin getting the hang of 
it . 




Judy, FN, Larry and Joe talked about receivers after 
the code practice session. 



"Good" was FN's comment, "now how 
about you, Joe?" 

"Well, FN, I haven't been able to get in 
as much time as Judy, with my paper route 
but I think were about even. IVe been con- 
centrating on the laws and regulations most- 
lv because a lot of the semi-technical stuff 
IVe had in physics classes and it comes 
pretty easy", 

"OK, then," said FN, "Larry ? what say 
you and I take turns asking them questions 
at random from the books? You take the 
license manual and I'll use the ABC's and 
we'll alternate the questions", 

'Fine" replied Larry, you start if off, FN". 

'All right; Judy suppose you tell me what 
the novice frequency bands are." No trouble 
here . , . Judy rattled them off like she 
was using them all every day, 

Larry came at her then with, "What is 



£t- 



it 



MARCH 1967 



25 



die maximum legal power allowed novice 
stations? 1 * to which she promptly replied* 
"75 watts" but Larry wanted more; "Input 
or output Judy?'* 

Looking a bit confused Judy countered 
with, "Input I think, isn't it? Gosh, I guess 
I didn't pay enough attention to that," 

*Tes 5 Judy" returned Larry, "input it is 
but remember you may get a question read- 
ing just that way'* * . . what is the maxi- 
mum legal input power , . "and if you were 
confused between 'input' and 'output* you 
could go wrong, Have Joe explain this to 
you more fully some time/* 

ll again being FN*s turn, he asked Joe, 
"What frequency bands can a novice use 
for radio telephony?** 

Joe immediately replied, "145-147 mega- 
cycles, only". 

After acknowledging this as correct, FN 
said, let's divert for a moment here; glad 
this came up* You're right Joe and the use 
of the word 'megacycle* may appear in your 
examination or a new term may appear 
here. Recently a change was mutually 
agreed upon by industry, educational insti- 
tutions and scientific organizations. The 
word liertz* was substituted for "cycles per 
second*, therefore megacycle has now be- 
come 'megahertz*, kilocycle is Tdlohertz' and 
they've made gigacycle "gigahertz*. Until 
the changeover is complete, your examina- 
tion questions may carry either expression; 
many of the current manuals and hand- 
books have not as yet been changed . . . 
this will take a bit of time. The change 
was made to honor the memory of Prof. 
Heinrich Hertz who is the acknowledged 
discoverer of the phenomena known as 
'Hertzian waves* or, as we have more com- 
monly referred to them, 'radio waves*, Just 
remember that if the word Tiertz' appears 
where you have studied it as 'cycles', they 
are one and the same. Ill give you each 
a card before you leave which shows both 
the old and the new designations and their 
abbreviations. Now let*s get on with the 
questions**. 

After about 45 minutes of this it was 
pretty evident to both FN and Larry that 
both youngsters had really done a bit of study 
ing. Several weak points cropped up of 
course and they were somewhat hesitant 
and unsure of the correct answer in reply* 
ing but in the main, Larry and FN were 
both satisfied that progress had been excel- 
lent. The kids were both cautioned not to 



relax their studies and FN would subject 
them to another informal verbal exam after 
they completed the code exam at the next 
bi-weekly session, Just then FN's XYL made 
her appearance with a heaping plate of 
freshly baked doughnuts and a pot of cof- 
fee, Joe went to the Honda for a six-pack 
of Coke and FN declared a recess. 

While relaxing with this bit of nourish- 
ment, Joe broke out with, "Gee, FN; some- 
thing Larry and 1 been wondering about 
for some time and always forget to ask 
you. We know what the TN* stands for 
. . your 'sine' or handle , * • but how come 
FN; why not your initials or some other 
letters?*' 

FN laughed and said, "Well it's not much 
of a story Joe. When I first went to work 
for Western Union as a student telegrapher, 
I was told that I must choose a two letter 
combination as my 'signature* to receipt for 
messages on the telegraph line. My initials, 
'DM' would have been all right except that 
one of the regular operators already used 
that sine. So I was told to choose any two 
letter group not then in use and my super- 
visor suggested something easily recognized 
and with good rythm, So, I finally came 
up with TN* which in the Morse telegraph 
code was easy to send and sounded rythmic 
, . . dit dah dit . . dah dit . , , that would 
be 'RN* in the radio code but when I changed 
over from wire to 'wireless' telegraphy, I 
was used to the letters FN and it was 
pretty rythmic in the Continental code as 
well; just one more dot, like this ... dit 
dit dah dit . . dah dit ... so I just carried 
it along and I ve been FN ever since". 

"Should Judy and 1 have sines too?" Joe 
inquired. 

"You can if you like Joe . . pick your 
initials or any combination that appeals to 
you but you'll find most hams and darned 
few novices will know what you mean when 
they ask your name and you say my sine 
is YZ* or whatever you have chosen. YouTl 
have to educate em to it . ■ most hams 
simply use their names. Yours Joe, is hardly 
longer than a sine would be . . just one 
more letter and an V at that so you really 
don't need a sine. On the other hand, Judy*s 
name is kinda long to send though not as 
bad as many that you'll hear, so if she 
wants to use a sine, nothing wrong with 
it. Her initials though are a bit long in code 
characters . . JM has a dot and five dashes 
in it . . she may want something shorter 



26 



73 MAGAZINE 



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and more rhythmic like DA or BR or some- 




** 



"How about BK, damps?" Judy broke 
in. 

"No" replied FN, "BK is a radio abbrevia- 
tion meaning "break' and it would be con- 
fusing; don't use anything which may have 
a double meaning like BT, AR, SK and such/' 

Judy pondered a few minutes and then 
came up with, "I'd tike to take the Con- 
tinental code equivalent of your sine Gramps > 
making it *R\ . , how about that?" 

Looking smugly pleased FN replied, "Sure 
- . it's OK with me; I don't think any of 
the boys will take you for a member of the 
Royal Navy or think you're a Registered 
Nurse" he finished with a chuckle. From 
there on out, Judy became *RN1 

With the little pick-up snack out of the 
way, FN reminded them that he had prom- 
ised to talk about the equipment they'd 
need for a novice station. "Let's start with 
the receiver; that's the first thing you 
should have and it wouldn't hurt a bit to 
get one right now. You could then listen 
to the many code practice stations sending 
slowly on the air and to novice and general 
class hams talking together. Most of them 
will be too fast for you but in straining 
to try and keep up you'll find that your 




code speed will build up a lot faster from 
the incentive provided by trying to grasp 
what they are talking about* Always prac- 
tice by trying to copy a station sending a 
little faster than you can receive solid; hell 
keep you on your toes". 

"Now there's several ways in which you 
can acquire a receiver" FN continued. "First 
off, you can build one from a magazine or 
handbook description, I don't recommend 
this for a beginner and I think Larry will 
go along with me on this" and Larry nodded 
in agreement "First off, today's ham bands 
are really crowded with stations. That means 
tli at you must have a 'selective receiver 
. , ■ one which will permit you to separate 
them as much as possible. This calls for 
what we know as a 'superheterodyne' re- 
ceiver or, as the hams call it more familiarly, 
a 'super-bet*; a good second bet is a really 
good tuned radio frequency type, again ab- 
breviated ham-wise to *TRF\ Building either 
of these is a pretty tricky procedure and 
after you have it all assembled and wired, 
it still must be 'aligned* which, to really 
do right, calls for several special instru- 
ments. In the long run you'll have a some- 
what mediocre receiver which will cost you 
about as much as if you had bought a good, 
standard make, already built and operating. 
Then too, you can compromise and buy a 
'kit* where all of the so-called Tiard work' 
has been done for you. Holes are punched 
and drilled in chassis and panel, coils are 
wound and roughly aligned etc. It's s 



Judy, Larry and Joe parted 



quite a fob to assemble, wire and complete 
the alignment. An experienced ham can do 
a good job with such a kit in a relatively 
short time but the beginner should be wary 
of tackling it," 

"Buying a good, factory-built receiver 
has several angles also. A really good new 
one by a reliable manufacturer is going 
to cost somewhere in the $150 to $250 
price range. Even better ones go up in price 
from several hundred dollars to a few jobs 
selling at a thousand or more! Don't let it 
scare you though; you are not about to 

[uip 'Gemini Control' but simply making 
a start in ham radio. You can do rather 

ell with one of the more modest receivers 
and if it's a fairly recent model of reliable 
manufactures it will bring a good trade-in 
value if and when you want something 
better later; home-built jobs are rarely ac- 
cepted as trade-ins," 

"Here's another approach , . the second 



28 



73 MAGAZINE 



hand market. Many hams who have started 
with modest gear eventually trade it in for 
something more elaborate or sell it at a 
substantial reduction. If of reliable make 
and it's appearance indicates that it has 
received reasonably good care, these can 
often be had for half or less than their 
original cost. Don't buy a pig in a poke* 
though; most hams are truthful and trust- 
worthy in deals of this kind but are often 
prejudiced as they have used the equip- 
ment for some time, are used to it's little 
idiosyncrasies and can handle it; a green 
buyer however could experience rather un- 
satisfactory results. By all means arrange 
to try out a piece of gear like this if you re 
considering buying it and preferably have 
a more experienced ham look it over and 
try it out . . . be guided by his opinion. 
Larry or I will gladly do this for you ■ . . 
many of your fellow club members would 
also be helpful here too, if you find some- 
thing you think is a good buy. Some of 
the mail order houses too, offer used equip- 
ment which they have taken on trade-ins 
and have had re-conditioned by their own 
technicians. World Radio Laboratories is one 
who specialize in this; there are a number 
of other reliable sources and you'll find 
them advertised in the ham magazines", 

"Another good bet in shopping for a re- 
ceiver is the military surplus offerings. Stores 
specializing in this as well as many mail 
order firms who advertise, still have a con- 
siderable amount of this kind of gear around 
at unbelievably low cost when you consider 
what fine pieces of gear they offer. Again 
you should rely on an experienced ham in 
helping you choose something which you 
won't have to modify extensively for ham 
band use/* 

Right here, Joe broke in with, "Say, FN 
a couple of years ago when I was doing 
a lot of short-wave listening, I picked up a 
surplus BC-312-N receiver down at Jim 
Turners' for thirty-five bucks. It sure is a 
well-built deal and really brings in short- 
wave broadcasts from all over the world. 
I often hear amateur radio phones at cer- 
tain places on the dial and the tiling is 
just loaded with all kinds of code signals 
but I don't know who they are. Could I 
use this receiver for my novice station?" 
"You sure can Joe and it's a dandy; I 
used one for several years before I got this 
little Davco solid state job I'm using now, 
The BC-312 is built like a battleship and 



is plenty sensitive and selective to pull ir 
ham signals from all over the world and 
you'll find it will fill the lull for you for 
a long time to come, right on into your 
general class operation- Only high frequency 
novice ham band you won't find on it is 
the 15 meter spread; the BC-312 covers 
the 20, 40, 80 and even the 160 meter 
bands in fine shape. When you reach the 
point where you tliink you'd like to play 
around on 15, you can build a simple con- 
verter to extend the range of the BC-312 in- 
to this band. So, you're all fixed with a 
receiver for a long time to come . . ■ how 
about you Judy?" 

"Oh, I'm not so lucky I guess; Dad's got 
some kind of an FM rig but it's no good 
for ham bands so 111 have to start from 
scratch" she replied, "Anyway I've saved 
a little money this summer from picking 
berries and a bit of baby-sitting so I guess 
thats' a good way to spend it". 

Larry chimed in with a suggestion that 
maybe Judy and Joe could take a look down 
at Jim Turner's and see what he might have 
in the way of a good surplus military re- 
ceiver or a second hand ham job. 

"If you kids turn up something that looks 
good, fll be glad to take a look at it and 
check it over for you. Jim will let you take 
it home and try it for a few days Judy, I 
know/' Both kids agreed to do a bit of 
Window shopping at Jim's place and the 
other two electronic stores in town and made 
a date for the 'great adventure* for the 
following week. 

With the receiver situation pretty well 
in hand now, FN suggested, "Let's call it 
quits for today then . . . it's about lunch 
time for all hands anyway. You young 'uns 
be out here two weeks from today, sharp 
at nine a. m. and we'll put you through 
your code exam. Don't forget now, write 
a postcard to the FCC and ask for your 
amateur radio operator license application 
forms, soon as you get home. Don't put it 
off or you may not get 'em in time - . . 
remember, FCC's mail basket is piled moun- 
tain high!" 

"OK Gramps" Judy replied, "we'll do it" 
and at Larrys invitation, they tied her 
bike on his rear bumper and she climbed 
in with him for the short ride home while 
Joe kicked the Honda starter and took off 
after a friendly wave and an exchange of 
the now familiar "73'* . . BCNU . . 

. . . WTOE 



MARCH 1967 



29 



™ 



Fred DeMotta W4RWM 
Post Office Box 6047 
Daytona Beach, Florida 



Going RTTY: Part Four 

Frequency Shift Keying 



The terminal unit is complete with its 
scope monitor and you have been getting 
fine copy. 

Now you desire to put a RTTY signal 
on the air and the question is— how? 

Let's first take another look at the termi- 
nal unit circuit described in December 73 
(1964), and add the mercury wetted key- 
ing relay. 

The addition to the circuit is the dotted 
lines in Fig. 1, and only the section of 
the original circuit covering the 6AQ5 is 
shown. 

This relay will permit you to key the 
transmitter through the keyboard of your 
machine, since depressing the keys on the 
machine will open the loop current and 
permit the relay to key the frequency shift 
keying circuit of the transmitter, and at 
the same time produce local copy on your 
machine. 

The mercury wetted relay shown is the 
WE276, although others will work as well, 
with the required socket changes* 

The only word of caution is that the 
mercury wetted relay must be mounted in 
a vertical position. 

Now that the modification is completed, 
let's look first to the use of frequency shift 
keying and a simple way of accomplishing 
it on the average transmitter. 

Let's see what we mean by frequency 
shift keying, assuming that we will employ 
the standard shift of 850 Hz, 

The terms applied to this difference in 



OUTPUT 



GAGS 





fr* 




t± 




J 



FSK 



) RELAV 
WE Z 76 H 



Fig, I. Adding a keying relay to the terminal unit 
described In the December 1964 73. 



frequency are MARK and SPACE, the first 
being the RF carrier and the difference in 
tliis MARK and the capacity introduced in- 
to the cathode circuit of the BFO, is called 
the SPACE signal 

To illustrate, let's take a frequency of 
7137 kHz. This would be the MARK signal. 
Now to shift this signal down 850 Hz would 
produce a SPACE signal of 7136.150 kHz. 

Now how do we accomplish the change 
in our MARK signal or the fundamental fre- 
quency of our transmitter? 

Fig* 2 shows a simple circuit which can 
be used with most transmitters and others 
with certain modification but the principle 
of creating the frequency shift remains the 
same. 

What occurs is that additional capacity 
is placed across the LC circuit of the oscilla- 
tor, which lowers the oscillator frequency 
sufficiently to move the transmitter carrier 
frequency 850 Hz. 

It should be pointed out that the MARK 
signal is always the higher of the two fre- 
quencies, so that the SPACE signal is shifted 
downward in frequency 850 Hz. 

The slug tuned coil (B) is made of 15-20 
turns of about 22 wire on a & inch form 
and tuned to an inductance of about 40 
mH, If you are unable to reach the 850 
Hz between the MARK and SPACE signal, 
vary the slug in a (B) slightly. 

In adjusting the shift pot it must be done 
slowly* observing the scope monitor for full 
deflection on both MARK and SPACE. A 
little experimenting with this adjustment 
will make for a 850-Hz setting. 

• . , W4RWM 



r 



tu 



.005 



RFC 
2.5 mH 



is) 





MICA 
.001 



/ 



SILICON 

DIODE 



TO CATHODE 
OF OSC* TUBE 



TO RELAY 

IN FIG. I 



Fig, 2, Simple frequency shift Iceyer adapter for a 
VFO. 



30 



73 MAGAZINE 




SUDDENLY YOU'RE WORKING MORE STATIONS . . . 



Knifing Through the QRM 

by choosing the optimum selectivity for 
conditions — a razor-sharp CW filter, a 
near-perfect SSB Mechanical filter, or a 
fine AM filter • . • 



Putting in the Weak Ones 

that demand the sensitivity of DAVCO 1 S 
exclusive Field-Effect front end . . . 

Blanking Out Noise 

from power lines and ignition with the no-extra-cost noise-blanker that lets you extract 
a Q5 signal you couldn't know existed without It . . . 

or nulling an offending carrier with the T-notch. The DR-30 communications receiver covers all the ham 
bands from 80 meters through 50,550 Mc in the 6-meter band. It has a built-in crystal calibrator, full 
AGC, Teflon wiring and plug-in modules for all active circuitry. It Is the most versatile receiver ever 
produced, and it can be operated from an AC pack or from batteries in fixed, mobile, and portable 

operations. 



Frequency coverage: 10 550 Ice segments covering 

the entire 80, 40, 20, 15, 10 meter ham bands 
plus 50,0-50*55 in 6 meters and 9*5-10*05 WWV. 
Provision for two extra ranges. 
Sensitivity: Better than .6 microvolts for lOdb s/n. 

Selectivity; SSB: 2 J Jtc Collins mechanical filter 
AM: 5 kc ceramic/transformer filter 
CW; 200 cycle crystal filter 

Stability: Negligible warm-up; less than 100 cps 
per hour; less than 25 cps for 20% power supply 
variation. Extreme resistance to shock and vi- 
bration* 

Detectors: Separate AM and SSB/CW product 
detectors; crystal-controlled BFO. 

Noise Limiter: True blanking action preceding 
selectivity; has separate ANL amplifiers and 
detector; front panel threshold controL 



RF Stage: Low noise premium Field-Effect RF ampli- 
fier and first mixer; tuned circuits employ high-Q 
toroidal inductors. 

Semiconductor Complement: 

23 bi-polar transistors 

2 Field- EfFect transistors 

10 signal diodes 

1 power diode 

2 lener diodes 

Size: 4'* high, T'/g" wide, 6" deep. Weight: 7 pounds 
Power requirements: 12 volts DC © 300 ma, 

maximum. 
Price: from factory „„.„. „ $389.50 

t/K"JU*SI Complete regulated power supply for 
operation of DR30 from 110/230 volts 50/60 
cps, plus battery holder for 9 D-size cells for 
portable operation; speaker, earphone [act. (Il- 
lustrated above) . „„, $39.50 



The DR-30 is fully compatible with any transmitter. 
At a cost equivalent to an accessory PTO, the DR-30 
gives the transceiver-equipped station an unequalled 
receiving capability. It is the appropriate nucleus 
for any amateur station. 



Send us your card for an information package con- 
taining evaluations of the DR-30 by the staffs of 

CQ (December 1966), QS7 (January 1967) and 73 
(May 1965)! an 8 page technical brochure and a 

complete schematic. DAVCO products are avail- 
able direct from the factory* 



DAVCO receivers for telemetry* radio astron- 
omy, WWV, SWL's and other special applica- 
tions are available from stock or can be 
provided to your specifications. Your inquiry, 
detailing your requirements, is invited. 




ELECTRONICS, INC 



P. O. Box 2677 
2024 South Monroe Street 
Tallahassee, Florida 32304 



Robert Sexton WB6CHQ 
2806 E. Norwich Avenue 
Fresno, California 



A Solid-State Product Detector 

Improve the performance of your receiver on SSB and CW with this simple 
transistor product detector. 



AH receivers not specifically designed for 
SSB reception suffer, to some extent, in 
quality and ease of tuning when used for 
this mode. Distortion of the received signal 
occurs for a number of reasons, When this 
includes BFO pulling, reduction of the rf 
gain may prove necessary. This in turn leads 
to loss of sensitivity and does not allow the 
AGC system to operate effectively. This is 
a less than satisfactory state of affairs. 

With the advent of SSB and the almost 
total disappearance of AM from die HF 
amateur bands, good SSB reception is man- 
datory. To date, a combination of hang- AGC 
and a product detector seems to be the best 
solution, The product detector is die most 
important element of this pair and num- 
erous articles have appeared discussing vac- 
uum tube versions of this worthy circuit. 
There has been very little information deal- 
ing with the design of a solid-state version, 
however. 

This article will describe a design which 
is a transistor equivalent of the popular 
dual-triode product detector. It will discuss 
the causes of distortion to SSB signals which 
include BFO instability as a result of pulling, 
AGC non-linearity and inter-modulation dis- 
tortion. As an example of these problems 
and their cure, it will refer to a product 
detector built for the Heathkit "Mohican", 



25V 




-O- V 



1H> 



cc 



AF OUT 



<>*— 1(— OBVQ IN 
33 pF 




Fig. I. Schematic of WB6CHQ r s simple product 
detector, Tke transistors are not critical; IR TR»06*s 
were used in the author's version, which was in- 
stalled in a Heath Mohican. 



In the GC-1A, the primary cause of dis- 
tortion to SSB signals is BFO pulling. This 
phenomenon is die direct result of the pres- 
ence of strong signals in the BFO circuit* 
In this receiver, the BFO output is injected at 
the input of the third if amplifier. This is done 
by connecting a 4.7 -pf capacitor from the 
collector of the second if to a tap on the 
BFO inductor. Thus, any signal in the if 
strip is also in the tuned circuit of the BFO 
to some degree. 

To understand why this will pull an oscill- 
ator, consider The tuned-grid, tuned-plat r 
oscillator. It may be shown that in this os- 
cillator, the tuned circuit with the higher 
"Q" will control die frequency. This is so 
because, a low "Q" tuned circuit having a 
broader frequency response, more feedback 
will be provided to the high "Q" circuit. 
Since feedback is the essence of oscillation, 
the tuned circuit getting the most feedback 
will control die frequency of oscillation. 

By applying this logic to the BFO, it is 
easy to see how pulling occurs, If the BFO 
is treated as if it were a TGTP oscillator, 
then the incoming signal can be thought of 
as a tuned circuit with infinite W Q'\ With 
this situation die closer BFO gets to the 
signal frequency, or vice-versa, than, of the 
two feedbacks present, that from the signal 
and diat from the BFO itself, the more pre- 
dominate the signal becomes. At some point 
in tuning, it becomes the controlling feed- 
back and the BFO shifts abruptly to the sig- 
nal frequency. 

When this occurs, the frequency differ- 
ence between the signal and BFO is neces- 
sarily zero. Since the desired audio output 
is that frequency difference, there can be 
no audio output. With an SSB signal, the 
peaks will be strong enough to pull the 
BFO leaving only the lower amplitude por- 
tions of the signal as output. The result is a 
highly punctuated garble, 



32 



73 MAGAZINE 



With a diode detector, an output of a 
different but still useless nature is possible. 
A diode is a non-linear impedance, that is, 
the impedance varies as a function of the 
applied voltage or current* A fundamental 
principle of electronics states that an AC 
signal applied to a non-linear impedance will 
generate harmonics of itself. If two fre- 
quencies are applied simultaneously, they 
will also generate their sum and difference 
frequencies. When a signal as complex as 
an SSB signal meets a diode, the result is 
only slightly less calamitous than the famous 
meeting of the irresistable force-and the im- 
movable object In this situation, every 
audio component present may mix with 
every other audio component to form still 
more audio components. The result is the 
muffled, quacking, semi-speech with which 
we have become familiar with the rising 
popularity of SSB, 

These components are also the output 
when the BFO locks onto one of the fre- 
quencies of an SSB signal But even if the 
BFO stays where it should, these components 
are still present in the output of the diode 
mixer, because the diode must mix all fre- 
quency components present. This is where 
the product detector has a distinct advant- 
age. It can mix only BFO and signal, rather 
than BFO and signal, signal and signal, eta 
This type of distortion will be recognizable 
to hi-fi fans as inter-modulation distortion. 

The AGC in a receiver can be another 
source of distortion. In receivers such as the 
GC-1A, AGC response is fairly fast, capable 
of following the syllabic rate of an SSB 
signal or the keying of fast CW- With a 
perfectly linear AGC, the only effect Oij an 
SSB signal will be uniform compression, or 
overall reduction of the dynamic range. If, 
however, the AGC response is not linear 
(which is likely since no tube or transistor 
has an infinite dynamic range, then the re- 
sult will be envelope distrotion. This is a re- 
arrangement of the relative amplitudes of 
the signal components. Normally, this dis- 
tortion is not too severe as most signals will 
stay mainly within the most linear portion 
of the AGC response, 

The more important problem with AGC 
is that, even without modification, it cannot 
be used effectively. If pulling occurs even 
with AGC, the AGC is not limiting the sig- 
nal sufficiently and the only recourse is to 
reduce the RF gain. When this is done, the 
AGC begins to lose control and its advant- 



ages are gone. It is worth noting that for 
the GC-1A, Heath recommends that it be 
turned off for SSB reception. 

Theory 

The product detector offers a solution to 
most of thses problems. It allows far better 
isolation for the BFO, reducing pulling to a 
bare minimum. Being a linear device, it does 
not experience the extreme inter-modulation 
distortion possible with a diode detetcor, 
Finally, since pulling is not a problem, it 
allows operation of the receiver at maximum 
rf gain and use of the AGC. Thus, neither 
the convenience of AGC nor the receivers 
sensitivity are sacrificed to the "new wave". 

The product detector is more properly 
known as a multiplicative mixer, the same 
circuit as is used for a converter in the front 
end of most modern receivers. This fact will 
explain the product detector circuits fre- 
quently seen which employ a pentagrid con- 
verter tube. Another apt name is "audio 
converter". 

To see why and how a product detector 
works, refer to the circuit of Fig. 1, First, 
note that the coupling capacitors used have 
a very high reactance for transistor work, 
even at 455 kHz, The reactance of the 
15-pF capacitor is about 20 kohm and that 
of the 33 pF is about half that. These high 
impedances are in series with the low input 
impedances of the transistors, providing a 
large voltage division* This insures small 
signal operation of the transistors guaran- 
teeing their linearity. 

This also provides a high degree of isola- 
tion for the BFO, which combined with the 
isolation inherent in the transistor, makes 
the BFO far more immune to pulling. This 
immunity is such that in the GC-1A, a local 
broadcast station about a mile distant, will 
not pull the oscillator more than about 50 
Hz, 

In operation, Ql is an emitter follower, 
whose vacuum tube corollary is the cathode 
follower. The same conditions hold true for 
both. They are capable of power gain, but 
not voltage gain. Since the emitter resistor 
is common to the emitter of both transistors, 
the signal is directly coupled to what is to it, 
a common-base amplifier. In this amplifier, 
voltage gain is dependent to a certain ex- 
tent on the quiescent or operating point of 
the transistor. This operating point is a func- 
tion of biasing and the bias may be con- 
trolled at the base. 



MARCH (967 



33 



15pF 









^Bfa^^^^M^^^ 



.■WK^sassK® 



gss 




0-V 



cc 



SIG, IN 




Since the BFO is connected to the base of 
Q2, it is constantly changing the bias and, 
therefore, the quiescent point at a rate near 
the frequency of the signal on the emitter. 
This means that the signal sees a linear in- 
put impedance and a rapidly changing volt- 
age gain. This is the reason for the term, 
multiplicative'. Since the output voltage is 
the input voltage multiplied by the voltage 
gain, if we must inlcude the BFO frequency 
to express the voltage gain in the equation, 
then the effect is literally multiplicative 
mixing. 

Adjustment and operation: 

This circuit is sufficiently simple that its 
construction should provide no obstacle to 
anyone* I have included the PC board lay- 
out (Fig. 2) that I used and one can see 
that I followed the actual appearance of the 
schematic quite closely. If you wish to make 
your own layout, this is generally the best 
method to follow, at least for the smaller 
projects. I strongly recommend that a PC 
board be used. They provide the neatest, 
most compact, best appearing and most dur- 
able form of construction available for small 
circuits such as this. Etching is not difficult 
and kits are available for it. 

Having constructed tihe circuit, it should 
be mounted in the receiver and connections 
made to it. The supply voltage may range 
from six to twelve volts but be sure that 
you do not exceed the collector breakdown 
ratings of the transistor you use. The BFO 
should be able to supply about .2 volts RMS 



05 k POT 



OAF OUT 



Fig. 2. Layout for the etched cir- 
cuit board used by WB6CHQ, 



OGND 

to the base of Q2 and the signal should 
not exceed this value at the base of Ql. 
These values are valid for the circuit when 
it is correctly adjusted. 

To adjust the product detector, first set 
the linearity pot to zero resistance (so that 
the base of Q2 is shorted to ground), With 
the BFO off, (making sure that the product 
detector is on adjust the linearity pot from 
zero until the signal to which your are tuned 
becomes slightly audible with the volume 
control on full. A local broadcast station 
makes an excellent test signal. When the 
BFO is turned on the signal should be very 
loud, though not quite as loud as with the 
diode detector for an AM signal. This will 
vary with the type of receiver but will 
probably hold true in most cases. If one 
wishes to tinker further, the ultimate de- 
sired result is a maximum of signal with the 
BFO on and minimum with it off. The signal 
present when the BFO is off is a result of 
intermodulation distortion and is not de- 
sired for best reception, 

When all this accomplished, it is possible 
that the BFO will need adjustment to get 
a zero-beat at the zero-beat mark on its 
control. In the GC-1A, this is remedied by 
tuning an AM signal for maximum on the 
S -meter, setting the BFO at the zero mark, 
and adjusting the BFO inductor for a zero- 
beat. Similar methods may be used for any 
receiver. 

In operation, the product detector is vir- 
tually identical to the diode detector with 
the major difference being the improved re- 
ception. The BFO is adjusted to one or the 
other side of zero-beat depending on which 
sideband is wanted- The signal should show 
the most deflection on the S-meter when the 
voice sounds the best The receiver may be 
tuned with the RF gain on full and the 
AGC on. 

The ideal SSB receiver is the one on which 
the only adjustment required is the tuning 
and sideband selection. When this product 
detector is used in the GC-1A or any other 
receiver, operation begins to approach that 
ideal. 

. , . WB6CHQ 



34 



73 MAGAZINE 



six meter SSB transceiver 



I 



the Heathkit SB-110...full features... new lower price-$299.00 



• The only truly high-performance SSB transceiver on 
six meters • Uncompromised engineering — the SB-110 
features the same quality crystal filter found on Heathkit 
80-10 meter SB-Series rigs • The same Heath LMO (Linear 
Master Oscillator) found on 80-10 meter SB-Series rigs 

• Built-in VOX • Built-in Crystal calibrator • Upper & 
Lower sideband selection • Full CW provisions, including 
built-in sidetone 



You Can Work "Six" With A Truly High-Performance 

Rig . . t get lowband stability* I kHz dial calibration, 
linear tuning, and a back laslv free dial mechanism, plus 
all of the other standard "built-in" features found on the 
Heathkit 80 through 10 meter SB-Scries equipment. The 
SB-II0 runs 180 watts P.E,P. SSB input, 150 watts input 
CW , . . considered the ideal transceiver power level by 
most ham radio communications engineers. It is one unit 
of the famous Heath SB-Series, meaning availability of 
matching low-band transmitters, receivers, and trans- 
ceivers, plus accessories such as the SB-600 Communica- 
tions Speaker, SB-630 station console, and SB-6I0 Signal 
Monitor. And the SB-II0 goes fixed or mobile with the 
appropriate power supply . , . the same versatility you 
experience with the famous Heath SB-IOK Call it the 
one "no compromise" six meter SSB transceiver* 



Kit SB-1 10, 23 lbs, .... 

Kit HP-13, Mobil* Power Supply, 7 lbs. . . 

Kit HP-El, Fixed Station Power Supply, 19 lbs. . 

Kit SBA-100-1, Mobile Mounting Bracket & lbs. 

Kit SB fiOO, SB Series Speaker, 5 lbs* 

Kit HS-24 P Mobile Speaker, 4 lbs, . 

HDP-21A, SSB 'Ham*' Microphone, 4 lbs.. . . 



FREE 
CATALOG 

Describes these and over 250 
kits for stereo/hi-fi, color TV, 
amateur radio, shortwave, 
lest CB, marine, educational, 
home and hobby. Save up to 
50% by doing the easy assem> 
bly yourself. Mail coupon or 
write Heath Company, Benton 
Harbor, Michigan 49022 



■ ■ ■ ft 



* * a a 



$£9100 
564.95 
549.95 
$14.95 
517J5 
S7.G0 
539.40 



PARTIAL SB-110 SPECIFICATIONS— RECEIVER SECTION: Sensitivity: 

0.1 yv for 10 db signal-plus-noise to noise ratio. Selectivity: 2.1 kHz (y: 
6 db down, 5 kHz mo>t,fei 60 db down. Image rejection: 50 db or better. 
IF rejection: 50 db or belter. Audio output power: 1 watt. AGC 
characteristic*: Audio output level varies less than 12 db for 50 db 
change of input signal level (0,5 uv to 150 uv). TRANSMITTER SECTION; 
DC power Input; SSB, 180 wolfs PEP; CW, 150 warts. RF power output; 
SSB, 100 watts PEP, CW, 90 watts (50 ohm non-reactive load), Output 
impedance: 50 ohm nominal with not more than 2:1 SWfL Carrier 
suppression: $S db down from rated output. Unwanted sideband 
suppression: 55 do down from rated output @ 1000 Hz & higher, Dis- 
tortion products: 30 db down from rated PEP output. Hum & noise: 
40 db or better below rated carrier. Keying characteristics: VOX 
operated from keyed lone using grid-block keying. GENERAL: Frequency 
coverage: 49,5 to 54.0 MHz in 500 kHz segments (50.0 to 52.0 MHz with 
crystals supplied). Frequency selection: Built-in LMO or crystal control. 
Frequency stability: Less than 100 Hz drift per hour after 20 minutes 
warmup under normal ambient conditions. Less than 100 Hz drift for 
±10% supply voltage variations. Dial Accuracy: Electrical, within 400 Hz 
on oN bond segments, offer calibration at nearest 100 kHz point. Visual, 
within 200 Hz. Dial backlash: No mare thon 50 Hz. Calibration: Every 
100 kHz. Power requirements: High voltage* +700 v. DC {g* 250 ma 
with }% max, ripple, Low voltage, -f250 v, DC @, 100 ma with .05% max. 
ripple. Bias voftage, — 115 v. DC @ 10 ma with .5% max, ripple. Filament 
vollage, 126 v. AC/DC® 4,355 ©mps. Dimensions: ^4^' W X h%* H x 




HEATH COMPANY, Dept, 11-1 

Benton Harbor, Michigan 49022 

D Enclosed is % 



Z Please send FR€E Heathkit Catalog. 



Name. 



I 
l 
I 
I 
I 

j City 



Please send model (s). 




plus shipping. 



(Please Print) 



Address. 



-Zip 



I 
I 



Prices & specifications subject to change without notice, AM-178 

«■■* obbp ow ^_ ^^ ^^ «■■■ ■■■> «■■■» «■■■ «■■■ «■■■ •■■%* •■■■ ■■■* ■■■» ■■■■ ■■■■ ■■■■ ■■■■■ ■■■»* •*■■■ ■>■■■ mhv ^— «■■» ^ 



AMCOM 



Robert Cox K3CEE 
1411 Medford Road 
Wynnewood, Pa. 



Amateur Mobile Communications 



The Phil-Mont Mobile Radio Club, Inc. of 
Philadelphia and vicinity is endeavoring to 
complete the outfitting of what it considers 
a communications facility second to none in 
AMCOM, Amateur Mobile COMmunications. 
This is being accomplished through the 
equipping of an independently powered mo- 
bile communications trailer t W3RQZ/ port- 
able, with its own prime mover also fully 
equipped to operate as an independent mo- 
bile relay station, W3RQZ/ mobile. 

Photo 1 shows the coin-truck, a 1949 In- 
ternational Metro, and the corn-trailer made 
by the Schulte Company in 1953, The truck 
was obtained from the Township of Spring- 
field, Delaware County, Pennsylvania, as a 
former bookmobile. It is now painted a 
bright emergency red, and well-marked as 
W3RQZ, Mobile Communications Center. It 
is well-known to Phil-M enters as the "Red 
Truck." The trailer was purchased from a 
contractor whose use necessitated minor 
body repair topped off with Rustoleum sil- 
ver paint. 

The emergency Red Truck contains equip- 
ment mainly for 10 meter AM operation, a 
60-watt unit with VFO and tunable receiver, 



and a 30-watt fixed frequency unit for op- 
eration on the club frequency of 29.493 
MHz. This unit can be operated at its posi- 
tion or by the driver of the vehicle. AC 
power can be supplied by an external gen- 
erator hauled in the truck. DC power is 
supplied by a 100-ampere Leece-Neville 
generating system. 

Two other operating positions are avail- 
able for 2 meter and 6 meter Gonset Com- 
municators, with ac and dc power cords in- 
stalled. The units are not permanently 
mounted in the truck, but are available from 
club members at a moments notice. 

Also included are two telephone line 
inputs for local and common battery lines; 
25 watt public address system which oper- 
ates on 6 Vdc or 110 Vac; automatic change 
over for lighting from ac to dc; metering 
of generator voltage, frequency and running 
time; handi-talkies on 29.493 MHz; galley 
supplies; vehicle and other tools; and local 
area maps. Antennas are available for all 
equipment, and are mounted in positions for 
minimum interference between bands. 

The communications trailer is Phil-Mont's 
most refined piece of emergency equipment. 




Photo I. The Phil-Mont mobile communications vehicles. On the left is the communications trailer, 
and on the right, the Red Truck, 



36 



73 MAGAZINE 




Photo 2. The message center position in the trailer. 

Twenty-six feet long, it is divided into an 
operating area 7' by 14' and a lounge area 
f by 12'. 

The operating area walls and ceiling are 
lined with accoustical tile and are fiber 
glass insulated. All interiors are white for 
light reflection, with dark green kick areas. 
Wall to wall carpeting completes the noise 
reduction. The lounge area includes a daybed 
for overnight operators, galley supplies for 
coffee breaks, and storage cabinets for gal- 
ley and stationery supplies. The lounge 
floor is tiled for easy cleaning. Each area has 
its own door, and eight windows around the 
trailer provide adequate ventilation when 
the IK ton air-conditioner is not in use, 

W3RQZ/ portable consists of seven oper- 
ating positions coordinated by a Message 
Center Chief, Stationed by the equipment 
rack at the door between the lounge and 
operating areas, the Message Center Chief 
accepts all incoming traffic originating at 
the portable operating site. He distributes 
the traffic to the proper operating position 
for transmission and keeps track of its prog- 
ress- From his position he has the capability 
of monitoring, recording or placing on public 



address both sides of any or all QSO's in 
progress, He can also patch any receiver to 
any push-to-talk transmitter, 

On the ceiling to the left of the rack is a 
power panel which distributes the power to 
the equipment, lights, and fans. It also pro- 
vides complete instrumentation of the volt- 
age, current, frequency, and running time of 
the incoming power. 

In the rack, from top to bottom, are; 
broadcast band monitor, NARCO VGTR-2 
for use on aircraft frequencies in emergency 
situations; message center patching and 
monitoring equipment; tape recorder; and 
public address amplifier. 

On the side of the rack is a control-head 
for 6 meter FM with an RCA CMV-3 on 
52.525 MHz and a telephone instrument 
for use with two incoming lines. Seen on and 
under the table are speakers and controls 
for several safety service receivers on both 
high and lowband police and fire frequen- 
cies. The binders contain complete schemat- 
ics for all equipment. 

Photo 3 is a view from the message cen- 
ter position toward the rear of the trailer. 
In it can be seen an SB-33 for 75, 40> and 
20 meter sideband; a 6 meter AM unit; and 
at the 10 meter position on the extreme right, 
an Elmac AF-67 and PMR-6. Either micro- 
phones and earphones or operator headsets 
are used with floor switches for maximum 
noise reduction and operating ease* 

Not shown is a Gonset Communicator II, 
modified for push-to-talk, and a Model 15 
Teletype for future use on 80 meter and 40 
meter FSK or 6 meter and 2 meter AFSK. 

Vertical antennas are available perma- 
nently attached for all frequencies but those 
below 14 MHz. For such frequencies coil- 
loaded mobile whips or portable wire- anten- 
nas are used. 

Before the acquisition of the corn-trailer, 




Photo 3, View toward trailer rear from the message 
centor position. 



MARCH 1967 



37 



Phil-Moat hauled portable power behind the 
Red Truck in a generator trailer constructed 
by club members. This trailer houses a 3 
kW— 110 volt Onan generator, Model W2C, 
water-cooled, two cylinder— four cycle, with 
electric start and ignition. The generator 
trailer is completely enclosed and has louv- 
ered access doors; power cords, junction 
boxes, jacks, wheel chocks, gas cans, and a 
power distribution panel complete the in- 
stallation. This unit is up for sale, but is 
hauled by other vehicles for present com- 
munications projects in the absence of a new 
Onan Model 305CCK, to be purchased by 
the club when funds permit* The new Onan 
will use propane as fuel and will be stored in 



the Red Truck or any other vehicle used to 
tow the corn-trailer, 

Phil-Mont is available with its two ve- 
hicles to undertake any communications ac- 
tivity, be it an emergency or a routine 
project; With a force of FhH-Monters active 
daily in their own mobiles on 29*493 MHz 
AM, 52,525 MHz FM, and 3.995 MHz SSB, 
practice in mobile communications is con- 
tinual, and leads them to say that Phil-Mont 
in ready "every single minute." 

Inquiries on particulars concerning Phil- 
Mont's vehicles should be addressed to 
W3QQH, C, R. Spencer, Jr., 124 Central 
Avenue, North Hills, Pennsylvania 19038. 

, . , K3CEE 



Improving the Ham M 



I am of the firm opinion that the Ham-M 
is the finest commercial rotator made . . , 
mechanically. It is very ruggedly built and, 
when properly installed, will not be the 
limiting factor, strength-wise, in any reason- 
able antenna installation, 

My complaint is with the direction indi- 
cating circuit. The meter in the control box 
is calibrated in 5* increments. And the sig- 
nal which the meter measures is the output 
of a low impedance voltage divider consit- 
ing of a wire-wound pot located in the 
rotor housing. What could be more accurate? 

The catch is simply that the bridge is 
driven by a dc voltage which is rectified 
from the ac line through a transformer and 
is directly proportional to it. What this 
means is that on a cold day when everyone 
is using their electric heaters, causing the 
line voltage to drop, my meter says that 
the antenna is pointed more to the west 
that on a "warm" day* Or, since I have poor 



mod^ieo ciRcurraY 

' 1 1 H i 1 1 H 1 1 ■ M 1 1 1 H I H I ■ 1 1 1 ■ 1 1 1 1 1 1 1 1 II 1 1 1 1 1 PM PIMM ■■ II ■ I ■ ■■ 114, 




^—03 



10 v. 



..Ill ■•■■IH44lt4n»MII 111 trill IHllM4IIHM<4 III IH'I llim III- 



Fig, I. Circuit of the Ham M control boi as mod 
tfied for consistent directional readings. 



line voltage regulation in the shack, when- 
ever I talk the linear up, the direction 
meter dips to the west 

A moment of head scratching convinced 
me that this nasty problem should be solved 
with only the most advanced techniques; a 
zener diode was called for, to regulate the 
indicator supply. 

A zener diode, you may recall, is the 
solid-state design engineer's answer to the 
VR tube. These little gadgets can regulate 
a voltage with a dynamic impedance of as 
low as 10 or less, far better than a VR 
tube, They come in lower voltages and 
a wider range, too. And this is the turning 
point of the story. 

The cover of the control box was removed, 
the zener diode and the three new parts 
shown in Fig. 1 were installed and the cover 
was replaced- A word of caution is in order 
about the installation of the zener diode. 
It should be connected "backward", that is, 
with the cathode wired to the positive line, 
Connecting the diode incorrectly can not 
harm any tiling; The only result will be that 
the output voltage will be less than a volt 
instead of 1.6 volts. The usual caution should 
be exercised with the electrolytic capacitor. 

The results have been most satisfactory. 
During more than eighteen months of op- 
eration, the full scale voltage of the bridge 
has been checked periodically and found 
to be right on the nose. And even better- 
when I talk the linear up, the direction 
meter doesn't budge a bit. 

. Galen Tustison WB6FGT 



■ « 



38 



73 MAGAZINE 



ADVERTISEMENT 




The Classic Feed System 



By W. E. "BARNEY" ST. VRA1N, W0PXE 

DESIGNING ENGINEER - CLASSIC 33 PROJECT 
MOSLEY ELECTRONICS, INCORPORATED 

4610 N, Lindbergh Blvd., Bridgeton, Mo. 63042. 



o 

o 

IB 

o 




INCE the introduction of multi- frequency 
beams several years ago, the method 
of feeding such antennas has been a 
subject of much disagreement. When these 
antennas were introduced a few years ago, 
Mosley Electronics ran a series of adver- 
tisements in the technical magazines ex- 
plaining the method used on our Trap-Master 
and Power-Master series. Since that time we 
have tried a wide variety of feed systems 
endeavoring to improve on the original sys- 
tem. 

Testing Other Feed Systems 

In testing, we found a three band gamma sys- 
tem ineffective without isolation networks 
which resulted in the feed system costing 
about equal to the antenna cost; with a 
system using hairpins, the cost proved low 
but did not provide a better match than the 
original Mosley matching system. It became 
quite clear to us, the Mosley system was 
hard to beat, for we had found only one 
slight disadvantage, the elements needed to 
be stagger tuned to raise the feed point re- 
sistance from about 30 to 50 ohms. This 
slight detuning, which proved advantageous 
in increasing the bandwidth, brought about, 
in turn, a slight gain loss of about 0.5 to 
1,0 db, at resonance. 

The Clossic-33 System 

In order to give hams a new choice in beam 
matching systems and an antenna featuring 
maximum gain with increased bandwidth, we 
devised the matching method used on our 
New Classic 33 antenna, a method which 
takes advantage of the principle that antenna 
resistance at the center driving point in- 
creases as the antenna length increases. 
Figure No. 1 shows the radiator element of a 
three element beam at resonance having an 
impedance at the driving point (Z A ) of about 
30 + JO ohms. If the element is made longer, 
Za can be raised to about 50 ♦ J50 ohms. 
(Figure No. 2) Since the reactance is induc- 
tive, it can be canceled with a series capac- 
itor of 50 ohms reactance, leaving 50 ohms 



feed point resistance. (Figure No P 3) Series 
capacitors used on the Classic 33 are made 
by inserting a suitable length of heavily in- 
sulated wire into each half of the element 
tube at the center. The wires are terminated 
in a plastic tube enclosure with a type - *N" 
connector for connection of the coaxial cable, 
To isolate the outer coax conductor from 
ground, the coax line is coiled for a few 
turns near the antenna end. This is designed 
to prevent the very unlikely affect of "Feed 
Line Radiation*'. 

Fig. 1. 



Z A = 30 + JO 



Fig. 2. 



L = T + 



50 -f J50 



Fig. 3, 



Mi 



50 + JO 



Converting Other Beams 

This feed system could feasibly be used on 
our other Trap-Master beams, but little would 
be gained and the antenna would need to be 
completely rebuilt. The big difference be* 
tween the new Trap-Master beam and the 
TA-33 is that the latter has conversion fea- 
tures, while the Classic 33 does not. The 
engineers at Mosley designed the Classic 33 
to give the ham a little extra gain on all 
bands* It is our conviction that discriminat- 
ing DX'ers will find this new tri bander 
specifically suited to their needs, but hams 
buying the well-known TA-33 will still enjoy 
a superior quality DX antenna with a gain 
very close to that of the Classic 33. 



Gordon Hopper Wl MEG 
75 Kendall Avenue 

Framingham, Mass. 



The Slide Rule Made Easy 



The slide rule is a great timesaver for anyone who needs to make a lot 
of calculations. Here f s a simple course in using one. 



Are you interested in improving your 
personal capabilities? Have you given any 
thought toward mastering the use of a slide 
rule? Did you, at one time, purchase a slide 
rule and then fail to follow through on 
learning how to use it? If the answer to 
any of these questions is yes, then here is 
your opportunity to get started on a simple, 
worthwhile project. 

Radio amateurs who are engineering or 
mathematic students, radio amateurs tak- 
ing electronic or mechanical refresher 
courses, and radio amateurs in the elec- 
tronic, electrical, or mechanical engineering 
professions readily realize the value of 
knowing how to use a slide rule. Radio 
amateurs who design their own equipment 
will find the slide rule to be an ideal time- 
saver when they become involved in mathe- 
matical processes. 

The person who does not use a slide rule 
for calculations is far less efficient than 
the person who does use one. For instance, 
without a slide rule, problems must be writ- 
ten out and the operations performed in 
lengthy detail by using the rules of ordinary 
arithmetic. This is very time consuming and 
the chance of making errors is very high. 
Sometimes a problem spreads over such a 
large area that die real point of the prob- 
lem is lost. Technical people find it to their 
advantage to be proficient in the use of a 
slide rule as every practical problem which 
requires a concrete answer will reduce to 
a mathematical computation. They find a 
great deal of time being saved while per- 
forming operations in multiplication, divi- 
sion, square roots, etc, on a slide rule and 
with h fairly high degree of accuracy. 

General 

What is a slide rule? It is a tool, or an 
instrument, designed to save time and labor 
for a person who is performing mathematical 
calculations. It is the mechanical equivalent 



of a table of logarithms* It is a ruler, a 
type of measuring stick which contains a 
number of graduated scales arranged in 
such a manner that multiplication, division, 
squaring, cubing, extracting roots , and other 
operations may be performed easily by the 
manipulation of the rule and the reading 
of the indications obtained on the scales. 

There are several types of slide rules 
available, and before purchasing one, the 
user should investigate further as to which 
one is best suited to his needs or purposes. 
Your technical associates, or instructor, can 
advise you as to which one will best satisfy 
your need. It is better to be advised in 
advance than to find out later that you 
possess a slide rule not satisfactory for your 
purposes. If you don't want to take advice, 
check a catalog and you will find at least 
five kinds oi slide rules available. Your 
own judgment may lead you to purchase a 
rule which is used by physicists or someone 
above the scope of your purpose. There are 
trig rules and beginners' rules. There are 
5-inch rules, 10-inch rules, and circular 
rules. So, be careful before you decide which 
rule to purchase. The vectorlog rule has 
27 scales and is generally used to solve 
problems in electrical engineering and 
physics. The dynamic reactance rule is used 
in calculations for decibel, inductive react- 
ance, capacitive reactance, resonant fre- 
quency, surge impedance, etc. The log log 
diipli-decimal trigonometric rule bus 21 scales 
including five log log scales and is used 
extensively when working with logarithms, 
A trig rule is usually satisfactory for most 
general amateur calculations, but working 
with advanced ac theory will require the 
use of a log log rule. 

Complete text books on the use of a slide 
rule are available and instruction books ac- 
company most new slide rules. This article 
includes condensed and simplified instructions 
for the fundamental and basic uses of a 



40 



73 MAGAZINE 







O 



ITATBH. 

X 



/ 



5TATOR 



/ 




CJRSOP 



H*»t_mE 








■ • 



-» j* lf i H l i iii |m i | iiii|ii ii| i in^ "iliIi|ili|iWmj —I 



3 



O 



^gj 



Rg. I. The major parts of a slide rule with the two most basic scales! the C and D scales. 



slide rule and should be beneficial to a 
beginner. 

Slide rule computations for use in elec- 
tronics are usually more accurate than the 
tolerances of the circuit components in- 
volved. A ten -inch slide rule will give re- 
sults accurate to within one part in 1000, 
or one-tenth of one percent when used cor- 
rectly . As a point of comparison, a good 
ohmmeter has an accuracy of ±2 percent 
and this will lead us to assume that for 
all practical amateur purposes, numbers used 
in slide rule calculations may be rounded 
off to a value which can be easily handled 
(significant figures). 

When working out problems involving 
ultra-high radio frequencies, the decimal 
point and powers of ten become involved, 
A person possessing a good knowledge of 
working with the powers of ten will have 
no difficulty in properly placing a decimal 
point when using a slide rule. 

You have now been introduced to the 
slide rule and it is necessary that you possess 
a slide rule in order to benefit fully from 
the remainder of this article, though Fig. 1 
illustrates the most common scales. 

Construction of the slide rule 

A slide rule has three major parts (see 

Fig. 1): 

( 1 ) the indicator^ or cursor 

(2) the slide 

(3) the stat or (upper and lower bars) 
Each scale on the slide or stators is 
identified by a letter (A, B, C, CI, GIF, 
CF, D, DF, K, L, LLO, LLOO, LL1 ? LL2 
LL3, S, ST, and T). There are two C, CI, 
and D scales so that the most commonly 
used scales will be available on either side 
of the rale. These scales are found on a 
log log rule and there will be fewer on a trig 
rule or on a beginners rule. 



If the user learns how to read the scales, 
how to set the slide and the indicator for 
each operation to be performed, and how 
to place the decimal point in the answer, 
it will then be a simple matter to multiply 
Slid divide, to square a number or find the 
square root of a number, to cube a number 
or find the cube root of a number, to find 
the logarithm of a number or find a number 
whose logarithm is known, and to find the 
sine, cosine, or tangent of an angle or to 
find an angle whose sine, cosine, or tangent 
is known. 

Interpreting the C and D scales 

The C scale on the slide and the D scale 
on the stat or are the scales most frequently 
used and are exactly alike. They are the 
fundamental scales of a slide rule and are 
used for all general fundamental calculations. 
Examine the D scale (Fig. 1) and you will 
see lines and large numerals printed on the 
stator (I, 2, 3, 4, 5, 6, 7, 8, 9). These 
lines are called primary graduations. The 
line labeled 1 at the right end of the C 
scale is called the right index, the line 
labeled 1 on the left end of the C scale is 
called the left index. The distance between 
1 and 2 on the D scale is divided into 10 
parts. These are called the secondary grad- 
uations (1, 2, 3, 4, 5, 6, 7, 8, 9). They 
are located between 1 and the primary 
graduation 2, To locate the numbers 12 
and 8 on the D scale— 8 is found at the 
primary graduation marked 8, 12 is found 
at the secondary graduation marked 2 (on 
the left). The number 14 is the secondary 
graduation marked 4 (on the left) and the 
number 19 is the secondary graduation 
marked 9 (on the left). The number 35 is 
found at the fifth secondary graduation to 
the right of primary graduation 3 (3.5 X 
10). The number 87 is located at tie seventh 



MARCH 1967 



41 



secondary graduation to the right of primary 
graduation 8 (8,7 X 10)- The increments 
of a secondary number are called tertiary 
graduations. For instance, on the D scale, 
the distance between 3 and 4 is divided 
into 50 graduations, each one having a value 
of 2, The number 3,6 is located 30 tertiary 
graduations to the right of primary gradua- 
tion 3, or 6 secondary graduations to the 
right of primary graduation 3, The number 
85,000 is located at the fifth secondary 
graduation (or the tenth tertiary gradua- 
tion) to the right of primary graduation 
8 (8.5 X 10 4 ), If you place the cursor hair- 
line at secondary graduation 2 on the D 
scale, you will be reading the number 12 
(•012, L2 5 120, 1200, eta). Place the cursor 
hairline at primary graduation 9 on the D 
scale, you will be reading the number 9 
(.009, .09, .9, 90, 900, etc.). 

Use of other scales 

The DF and CF scales are the same as 
the D and C scales except that they are 
folded at tt (3.14). To avoid the necessity 
of resetting when an answer runs off the 
scale, they are used with the C and D 
scales, The CI scale is an inverted C scale 
used in reading the reciprocal of a number. 
The Dl scale is an inverted D scale the 
same as the CI scale. The GIF scale is 
an inverted CF scale used with the DF 
scale in the same manner as the CI scale 
is used with the D scale, The A and B 
scales are identical and are used with the 
C and D scales when finding squares and 
square roots. The K scale is used in finding 
cubes and cube roots, The S scale is used 
when working with the sine and cosine of 
an angle. The T scale is used when work- 
ing with the tangent of an angle. Trig slide 
rules may have a T2 scale for working with 
tangents of angles greater than 45°. The 
ST scale is used when working with sines 
and cosines of angles less than 6°. The L 
scale is used with the D scale for finding 
the mantissas of the common logarithms. 

Simple multiplication exercises 

Get familiar with using the slide rule by 
calculating simple problems first. The easiest 
function to perform first is the multiplica- 
tion of two numbers, Set the left index 1 
on the C scale (slide) to line up with the 
primary graduation 2 on the D scale. Move 
the cursor hairline to the primary gradua- 
tion 2 on the C scale and read the result 



(2 X 2) on the D scale as being the num- 
ber 4 (20 X 2 = 40, 20 X 20 = 400, 2000 
X 2000 = 4,000,000, .02 X .2 = ,0004, etc). 
Set the right index 1 on the G scale (slide) 
to line up with the primary graduation 8 
on the D scale. Move the cursor hairline to 
the primary graduation 7 on the C scale 
and read the result (8X7) on the D scale 
as being the number 56 (.8 X .7 = .56, 80 
X 70 = 5600, .08 X ,07 = .0056, 800 X 
700 = 560,000 , etc.). 

Simple division exercise 

Division of numbers on a slide rule is 
the opposite or inverse operation of multipli- 
cation. To divide 8 by 4, move the C scale 
(slide) until 4 is lined up with 8 on the 
D scale and read the result (8/4) found 
at the left index point on the D scale as 
being 2 (.08/.4 = ,2, 800/.004 = 2000,000, 
etc) 

Multiplication of three numbers 

Multiplication of three numbers is a litde 
more involved than with two numbers, but 
is not complicated. Multiply 28,5 X 4*6 X 
6 as follows: make an approximation— 30 
times 4 times 6 = 720. Set the right index 
1 of the C scale to line up with 2.85 on 
the D scale. Set the cursor hairline at 4,6 
on the C scale* Set the left index 1 of the 
C scale under the hairline. Read the result 
on the D scale directly below 6 on the 
C scale as 790, Practice will improve your 
accuracy. 

Multiplication and division combined 

Find the product of two numbers and 

divide the result bv another number. 

- 24 x 38 A 

Irtj — Tq~a — An approximate answer 

could be 8. Set 12.4 on the C scale to line 
up with 2.4 on the D scale- Move the cursor 
hairline to 3.8 on the C scale and read 
the result on the D scale as 7.35. 

Simple proportion exercises 

Here is the easy way to find proportions. 
Find x if 2/3= 5/x. Place 2 on the C scale 
directly over 3 on the D scale. Move the 
cursor hairline to 5 on the C scale and read 
the result on the D scale as 7.5. Find x if 
18/x = 3.5/22. Place 3.5 on the C scale 
directly over 22 on the D scale. Set the 
cursor hairline to 18 on the C scale and 



42 



73 MAGAZINE 








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Name 



Call 



Address 



City 



State 



Zip 



read the result on the D scale as 113. 

Circular measure exercises 

Convert *72 radians to degrees; Set 2 
on the C scale directly over the ir mark 
on the D scale. Move the cursor hairline 
over the left index 1 on the C scale and 
read the answer on the D scale as being 
L57 degrees. Convert 45* to radians. Place 
R (or P°) on the C scale directly over 4.5 
<>n the D scale. Read the result on the D 
scale directly below the right index 1 of the 
C scale as ,785. We know it will be less 
than 1 because 1 radian is equal to 57,3 

degrees. 

Simple trigonometry exercises 

It is very easy to calculate circle circum- 
ference and diameter. Here we use the D 
and DF scales. Find the circumference of a 
circle having a diameter of 4 cm. Place 
the cursor hairline at 4 on the D scale 
and read the result on the DF scale— 12.57 
cm- Find the diameter of a circle having 
a circumference of 50 cm. Place the cursor 
hairline at 5 on the DF scale and read 
the result on the D scale— 15,8 cm. 

Squaring and square ar cube roots 

Likewise, squaring numbers and extract- 
ing square roots turns out to be very easy. 
To square the number 3.3 5 set the cursor 
1 mil line to 3,3 on the D scale and read 
the result on the A scale— 10.9, Find the 
square root of 40. Sot the cursor hairline 
to 40 on the A scale and read the result 
in the D scale— 6.3. The K scale is set 
up h\ three sections, Use the left section 
for finding the cube root of numbers be* 
tween 1 and 10, the middle section for find- 
ing the cube root of numbers between 10 
and 100, and the right section for finding 
the cube root of numbers between 100 and 
1000. Find the cube root of 8* Set the cursor 
hairline to 8 on the left section of the K 
scale, read 2 on the D scale. Find the cube 
root of 80. Set the cursor hairline to 8 on 
the middle section of the K scale, read 4.3 
on the D scale. Find the cube root of 800, 
Set the cursor hairline to 8 on the right 
section of the K scale, read 9.3 on the D 



ale. 



Logarithm exercises 

A slide rule reads only the mantissa of 



common logarithms and the characteristic 
is to be calculated. Find logic 3,14. Place 
the cursor hairline at 3.14 on the D scale. 
Read the result on the L scale directly un- 
der the hairline as 0.497, Find logw 887. 
Place the cursor hairline at 8.87 on the D 
scale. Read 0,948 on the L scale. Add the 
characteristic 2 and the answer is 2.948. 

Working with the 
trigonometric functions 

Trigonometric functions are readily de- 
termined by the use of a slide rule* Work- 
ing with these functions involves the use 
of the C, CI, D, S, T, and ST scales. Exam- 
ination of the S, T ? and ST scales shows 
each identified graduation as having a 
double set of numbered graduations. On the 
S scale, which will be used with the C or 
D scale, the left hand (black) graduations 
are angles between 5,7° and 90* to be used 
with sine value calculations. The right hand 
(red) graduations are angles between 5.7* 
and 84° to be used with cosine value cal~ 
dilations. Find the sine of 15°. Set the 
cursor hairline to the black 15 on the S 
scale and read 0,259 on the D scale. Find 
the cosine of 60°. Set the cursor hairline 
to the red 60 on the S scale and read 0*5 
on the D scale. If the sine value is 0.96, 
what is its angle? Set the cursor hairline 
to 9.6 on the D scale and read 74° on 
the S scale. On the T scale, the left hand 
(black) graduations are angles between 5.7° 
and 45° to be used with tangent value cal- 
culations. The right hand (red) graduations 
are angles between 45° and 84.3* to be 
used with cotangent value calculations. The 
tangents of angles between 5.7° and 45* 
are read on the C or D scale and those 
between 45* and 84,3° are read on the CI 
scale. Cotangents of angles between 45* 
and 84.3* are read on the C or D scale 
and those between 5.7* and 45* are read 
on the CI scale. Find the tangent of 31°, Set 
the cursor hairline tn the black 31 on tl 
T scale and read 0.6 on the C or D scale. 
Find the tangent of 70°, Set the cursor 
hairline to the red 70 on the T scale and 
road 2.75 on the CI scale. The ST scale 
is used when working wilh sines and tan- 
gents of angles between 0,5° and 5.7°. 

The author used a Lafayette 99-7031 10- 

- 

inch luti log dupli triti slide rule in tin 
above trig function manipulations, More 
detail could be given towards this type of 
coverage, but since not all slide rules are 



44 



73 MAGAZINE 



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• NO APPRECIABLE DISTORTION 

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• TALK POWER GAIN AT LEAST lOdb 

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• INSTALLS IN MICROPHONE LEAD 

• ALL SOLID STATE PRINTED CIRCUITRY 



NEW 

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A prototype of the CSP I I has proved itself an effective communication aid on the amateur bands 
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the unit will enhance the intelligibility of voice signals considerably under difficult conditions, 'MIL' 
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alike, it would benefit the user more to study 
the examples given in the book which accom- 
panies each new slide rule. 

Log log scales 

The LL scales on a log log rule represent 
a logarithm of a logarithm. The LL1, LL2, 
and LL3 scales range in values from 1.01 
to 20,000, are used with the C and D scales, 
and give the natural logarithms of num- 
bers greater than unity. The LLO and 
LLOO scales range in values from 0,0001 
to .999 ? are used with the A and B scales , 
and give the natural logarithms of numbers 
less than unity. 

Using tke c, P°, and ~ gage marks 

Near the left end of one C scale and 
near the end of one D scale you will note 
the small letter c. This represents 1*128 
and is used when calculating the area of a 
circle. Find the area of a circle having a 
diameter of 1,4 cm, Set the cursor hairline 
to 1,4 on the D scale which does not have 
the letter c on it, Place the letter c on tire 
C scale under the hairline. Move the cursor 



hairline to the C scale left index. Turn 
the slide rule over and read the area on 
the A scale under the hairline as 1.53, The 
P° mark found on one of the C scales and 
on one of the D scales represent 5,72958 
and is used when converting an angle from 
degrees to radians. The tt mark found on 
the C ? D > CF, and DF scales represents 
3.1416 and is a ratio of the circumference 
of a circle to its diameter. 

Conclusion 

Much more could be written about the 
use of a slide rule but tills article is pre- 
sented with the hope of inducing amateurs 
to become familiar with the benefits to be 
gained by using a rule. More difficult exer- 
cises and information pertaining to the care 
and maintenance of a slide rule are usually 
contained in the book which accompanies 
a new slide rule. After some concentrated 
practice, one should be able to multiply, di- 
vide, handle square and cube roots, and 
some of the trig functions very easily. For 
those who wish to go further, it is recom- 
mended that they obtain a textbook cover- 
ing all of the uses of a slide rule. 

. . . W1MEG 



MARCH 1967 



45 



■■ 






«sl 



Jim Ash© W2DXH 
R.D. I 
Freeville, N. Y. 



How to Make Better Panels 



Do all of your construction projects seem to look horrible? Here are 
some good hints that will help you make them attractive* 



What does your home made gear look 
like? If your work resembles much of mine, 
you may not be too eager to show it to 
the public eye* For some time I've used a 
simple ink-marking process on bare alumi- 
num which is adequate but harsh and prone 
to glare. It was passable, but I felt per- 
sistently unhappy about its overall appear- 
ance. This article describes one of the ways 
I finally worked out for making more satis- 
factory panels. 

You won*t need any special tools or ma- 
chinery. There are no chemical processes, 
although some time is required. The finished 
panels can be very colorful, and a few of 
mine are* Ten dollars should put you in busi- 
ness for the next two years or more, and 

the finished panels really do look goodl 

■ 

Materials Required 

1, A scraping knife, a rather fine file, 
and some emery cloth. 




2* A sheet of fine grade wet sandpaper. 
A fine-textured abrasive on waterproof 
backing, used wet* The water prevents re- 
moved metal from building up little islands 
which clog the paper. Try some dry and 
see. 

3, Kitchen detergent, stronger varieties 
preferred. 

4, Denim rag. 

5, Large cardboard box and some cheese- 
cloth, scotch tape and safety pins, 

6, A few odd pieces of brick, wood, or 
pipe, 

7, Rust oleum spray enamel, about $2.00 
per can. Their + 975 gray is good to start, 
and you might like to purchase other light 
colors later. 

8, Draftsman's lettering supplies: ruler, 
penSj and waterproof India ink. 

9, Rustoleum #717 clear spray enamel. 
Purchase emery cloth and wet sandpaper 




These are the materials used in making panels. Most 
of them are very easily obtained from local hard- 
ware stores, supermarkets, and bookstores. 



Choose unpainted metal parts for construction, and 
save yourself the trouble of cleaning off the manu- 
facturer's inexpensive soft paint. 



46 



73 MAGAZINE 







Simple spray booth. Maybe ten cents in materials. 
Store it front down to keep dust out. 



which feels abrasive but not toothy to the 
touch. Different manufacturers use differ- 
ent grading systems so I haven't recom- 
mended a particular degree of roughness. 
Since you're not going to really lean on it, 
the scratches won't be deep and the grade 
you use is not critical. 

Preparation 

If you want a good job, the surface to 
be painted must be real clean. You have 
two foes: grease and dust- Grease spoils 
paint adhesion, and dust results in a relative- 
ly huge mound in the finish for each tiny 
particle, I hope you'll begin by practicing 
on some scrap metall 

Surface preparation starts with the pur- 
chase of the chassis or panel that is to be 
painted- Choose aluminum with a natural 
or unpainted finish. This saves solvent prob- 
lems or a trip there and elsewhere for 
somebody who can get it off for you. 

You can make guide scratches on the 
panel surface during construction. But they 
mustn't be deepf Although Tve never tried 
it, I suspect a good epoxy auto body filler 
could fill in some pretty deep gouges. An 
ordinary nail is hard enough to take a good 
point for working on soft aluminum, and 
will not need frequent resharpening. 

When the construction work is done, go 
back over the chassis or panel to clean up 
the edges, corners and holes, A good knife, 
used carefully, will pare out the rough 
edges that usually appear around holes. A 
fine file can round off sharp comers and 
feather edges left by dull shearing tools. 
You may want to give the work a first 
finishing from a small piece of emery cloth* 

Then make up a strong detergent solu- 
tion and wash the work thoroughly. Use a 




y0. 





This piece of scrap metal was cleaned over all and 
then sanded on the upper portion only, before paint- 
ing. Test scratches made with the edge of a sharp 
knife show good adhesion on the sanded part. 

wad of denim as a washcloth, and scrub 
all surfaces twice, whether they get paint 
or not. This removes grease which could be 
carried around to the painted surface just 
ahead of the enamel. Rinse thoroughly, and 
by now your hands should be very clean 
too. 

Still using warm water, have a go with 
wet sandpaper at the surfaces to be painted. 
Use only moderate pressure. Rub up and 
down, diagonally, crosswise, and in circular 
directions. The surface should take on a dull 
whitish-metallic sheen with no strongly pre- 
ferred direction of marking. The enamel 
sticks very well to metal surfaces treated 
in this way, so that no primer is required, 
I've tried it both ways. 

When you're done with this, shake off 
the excess water, wipe with clean paper 
towels, and put the work in a warm place 
to evaporate the last traces of moisture. 
When dry, wrap it in a clean newspaper 
and you can store it without deterioration 
of the surface. 

If you're in a hurry, you can shortcut 
the following process by marking directly 
on the cleaned surface with India ink. Then 
spray clear enamel over all. Or you can 
apply clear fingernail polish over the labels 
and have your work back on the assembly 
bench in about a half hour from starting. 

Spray Painting 

Try to arrange things so you can do the 
entire job without moving the work. If you re 
painting a box or other many-sided surface, 
think about how you will move it when it's 
wet. You'll soon accumulate a few wood 



MARCH 1967 



47 






X 





Take this with you when you go looking -for lettering 
supplies* Here are a pen holder, a Leroy adapter! 
one of the Leroy lettering tips, and a very convenient 
ink dispenser. 



blocks and other objects for propping tilings 
in place. A panel or chassis will rest nicely 
on top of a piece of pipe and can easily 
be rotated to get at all sides. 

The Rustoleum enamels I've been using 
are well behaved, and flow very nicely a 
few seconds after going onto the metal. 
The object is to get just enough every- 
where to cover the work. Avoid overdoing 
by putting on a coat that's visibly too thin. 
Estimate your progress and then put on a 
little more. Corners seem to need special 
attention. 

Those handy spray cans will generate an 
awful mess. I don't think spraying outdoors 
is practical, so here is a way to keep the 
stuff under control. Find a cardboard box 
fifteen inches or more deep and large 
enough so your work doesn't seem cramped 
in it. Put in three or four layers of cheese- 
cloth a few inches from the closed back. 
Scotch tape will do the job and a few 
safety pins may help. With some news- 
papers over the adjacent bench, you will 
have a spray booth that works much bet* 
ter than you'd believe without trying it. 
The cheesecloth reduces the disturbance of 
spraying and catches most of the waste 
spray. 

The Rustoleum people suggest spraying 
from a distance of a foot or so. Start the 
spray off target, and then swing it across 
the work. Keep it moving! Spray, check, 
and spray again. With practice you can 
learn to paint a vertical surface with little 
or no bead developing along the bottom 

edge. 

You'll find a little note on the spray 



- 1 i i ■ r-j 



lilUiiUJ 




Closeup of a convenient scale for drawing guide- 
lines. Two parallel guidelines included. 



can about cleaning the nozzle when you're 
done spraying. I have a three-year old can 
of spray which works fine. Another didn't 
get cleaned properly some time, and it doesn't 
work so well. Be sure to clean the nozzle 
as per instructions! 

When you're done spraying, get right away 
horn the work. Come back next day. Some 
heat will help things along if you're in a 
hurry. But this will increase the chance 
of dust, dirt or damage. I have done the 
complete job in one day, but a slower ap- 
proach will give nicer results. 

When the work has dried sufficiently, 
almost anything that will apply ink to paper 
will serve for labeling. I generally use a 
Leroy pen set. Bookstores, paper supply 
houses, and many other businesses carry 
drafting supplies which may be usable. Try 
Speedball products. Lettering jigs and guides 
that work well on drawing boards are less 
successful on real panels with their holes, 
screw heads and other obstacles. 

Why not learn draftsman's 
Good books on drafting devote 
or two to the subject, or little, 
pamphlets come complete with neatly marked 
practice pages. One of these is well worth 
50c or so. Practice a little bit every day 
. , . you will find yourself using your neat 
new lettering on schematics, notes, and 
other applications as well as shiny fresh 
panels. 

Rough out your panel before you mark 
it up. Almost every time I omit this simple 
step I regret it. Just make up a freehand 
sketch about full size and write the letter- 
ing on it in pencil. Revise until it looks 
right to you. Don't get fouled up in rules 
of proportion and all that. 



lettering? 
a chapter 
soft-cover 



48 



73 MAGAZINE 



Then you re ready to put lettering guide- 
lines on the panel. A dull-pointed tool, 
which will scratch but not penetrate the 
soft enamel is required. If not overdone, 
these lines will disappear when you apply 
the clear finish coat. A nail will take a 
good point, use it gently! A transparent 
five-and-dime ruler with parallel guidelines 
on it serves to get your parallel lines in 
place. The lines should be just strong enough 
to be visible through the ruler. Wash the 
ruler just before using, and keep fingers 
and hands off the panel. A handy sheet 
of paper enables you to rest your hand 
where convenient, 

I use a Leroy pen for lettering. You'll 
probably want to start with a #1 and a 
#3 point, and pick up a #0 and a #2 
later. These odd-looking devices are very 
good once you get used to the loose piece 
in the center. This serves to keep the tip 
from drying rapidly, as it does in a con- 
ventional pen. If the tip does seem dry, 
jiggle and rotate the center piece til the 
ink flows freely. The flattish working ends 
are relatively immune to digging into the 
work. 

Choose the larger point for larger letter- 
ing to avoid a spidery appearance. Mount 
the pen in the holder and go at the panel, 
just as in practice with a pencil. If you 
can't make out the guidelines, change the 
lighting a little bit. They should be just 
visible as white against darker, rather than 
the usual dark against light seen on paper. 

If you make a booboo, and we all do, 
a handy Kleenex dampened with a little 
spit will rub out the mistake. Then blow 
some humid breath on the panel, and wipe 
off the fogged region with a piece of 
dry Kleenex, Do this one or twice more, 
Tliis gets the last traces of spit off, so the 
new lettering is the same weight as the 
uncorrected lettering nearby. If you don't 
do this, it will be heavier. 

A grease contamination far too thin to 
see will spoil the fresh enamel's excellent 
wetting properties. Have a few pieces of 
clean paper handy and keep most of the 
panel covered while lettering, You may get 
so involved with neat lettering your hand 
wanders off the protective paper. Sorry 
about thatl 

When the lettering is finished, set the 
panel aside to dry for a few minutes to a 
half hour before going on to the clear 
enamel finish coat* 




This panel was completely finished in one day. Slight 
crinkling of the finish at one point probably does 
not show in magazine copy of photo. 

Finishing up 

I once applied lettering and finish coat 
eight hours after enameling, with the help 
of heat for quick drying. But I recommend 
a drying period of at least 24 hours in a 
warm place. Try your luck on some scrap* 
If the color coat is insufficiently cured, it 
will wrinkle free of the metal when the 
finish coat goes on. 

After the finish coat has hardened for 
at least 24 hours, youVe ready to go ahead 
with final assembly of the project. Be nice 
to the fresh, soft enamel! If you wash your 
hands and wipe tools with a paper towel 
just before starting work, the whole project 
will stay quite surprisingly clean. 

As a nice final touch, if you want to 
wait at least another 24 hours, the enamel 
will take a coat of auto body wax, Car 
painters like to have you wait a month or 
more, and I think they use materials similar 
to mine. Well, this wax finishing really 
puts the grand touch on. You'll be very 
pleasantly surprised at your results, and it 
really is worth the time it takesl 

. W2DXH 



• • 




Another simple panel. Oops, seems to be a breed- 
board in there. 



MARCH 1967 



49 






E. C. Reich W5FQA 
3806 Norma 
Garland, Texas 



An Automatic Keyer Using 



Intergrated Circuits 



Here's a very simple integrated circuit keyer that uses very few parts. 



This article describes one of many possible 
applications of integrated circuits to ama- 
teur radio. The keyer described is self com- 
pleting, completely adjustable from less than 
one word per minute to sixty words per 
minute, and could be built in a pocket 
match-box. The complete keyer can be built 
tor less than thirty dollars ($30.00). 

Operation 

A clock generator consisting of a uni- 
junction transistor and an R-C combination 
is used to determine the speed of operation. 
The basic relation of a space equals a dot, 
and a dash equals three dots was used and 
is constant regardless of the speed. The 
clock pulse is connected to the dot flip flop 
through the logic built into the flip flop 
package. The output of the dot flip flop 
drives the dash flip flop. The output of 
both flip flops are connected to a gate 
which has an output if either of the inputs 
go to zero. 

The output of the gate in this keyer is 
used to drive a transistor to control a relay. 
It is possible to use a transistor only and 
build in weighting circuits to give individual 
desired effects; but, the emphasis of this 
article is on the application of the inte- 
grated circuit, 

Texas Instruments integrated circuits were 
available at reasonable prices and were 
chosen for this application. The SN7302 
package (.125 X .250 X ,035 inch) con- 
tains two flip flops and all of the necessary 
logic circuits required for proper gating. 
(38 transistors total) The SN7360 quad- 
ruple two input NAND/NOR gate contains 
24 transistors total in the same size pack- 
age. Only one of the four gates in this 



package is used. 

The integrated circuits operate on 3 to 
4 volts dc. The minimum voltage which will 
operate a unijunction transistor properly is 
9 Vdc } therefore, a 5p6-volt zener diode is 
used to drop from 9 Vde to 3.4 Vdc* The 
zener diode was chosen over a divider in 
order to maintain a low power supply im- 
pedance for the integrated circuits. 

Circuit description 

Refer to the schematic diagram. Fig. 1, 
and the logic chart, Fig. 2. The capacitor C3 
charges up at a rate determined by the 
speed control Rl and R3. When the voltage 
across C3 reaches the intrinsic stand-off 
ratio of Ql (firing point) C3 is discharged 
through R4. This provides a positive pulse 
several milliseconds long with an exponen- 
tial decay- The flip flops trigger only on 
the trailing edge of the clock pulse so this 
signal is passed through C5 and R5 to pro- 
vide a fast rise and fall pulse. 

The terminals marked on the schematic 
with an asterisk are the dot flip flop* The 
flip flop operation is as follows: Q. HAS A 

2*5 V. output and Q* (pronounced not Q) 
is at zero. If K. is positive when a clock 
pulse is applied to CP* the flip flop switches 

and Q. and Q. switch modes. Since J* is 
connected to +3 volts the following clock 
pulse reset the flip flop to its original 
mode. This action represents a dot and 
space. If the dot key is held down the next 
clock pulse simply triggers the flip flop 
again and if the key is released the next 
pulse resets the flop flop to a space con- 
dition and it remains. 

The terminals of the SN7302 without an 
asterisk are used for the dash flip flop. 



50 



73 MAGAZINE 




CR3 
IN 4734 A 



TO *MTR 



C2 



* 



f 



CR4 
IN400I 



CR3 
IN400I 



9V 



<HHr 



13 



es 



FFI 

SN7302 
(DUAL FLIP- FLOP J 

QP Q» Q* Q 



C-J 



- 



Hfcd 



* 



50 pF 



/T7 



R4 

100 



R3 
£20 



R6 
820 



* 



S 





r 



JHYI 



^ 



J 



t + 3 



Gl 

(GATE) 



t-J 



R8 
4.7 k 




Q2 
2N37U 



Fig. 1. Schematic of WSFQA's integrated circuit keyer. 



The dasli operation is as follows: The key 
is moved to the dash position and a positive 
voltage is applied to K. through CR1 start- 
ing a dot sequence. Q+ goes positive at the 
start of the dot. This positive signal is dif- 
ferentiated by C4 and R6 providing a fast 
rise and fall pulse at CF. (The clock pulse 
input for the dash flip flop,) The input 

at CP triggers the dash flip flop causing Q 
to go positive since K is positive. The next 
clock pulse triggers the dot flip flop, but 
it will not trigger the dash flip flop until 

Q. goes positive again which is the follow- 
ing pulse. Then the dash flip flop changes 
state, but the output of the dot flip flop 
is still present and will remain for the 
length of a dot which gives a dash length 
of 3 dots. If the key is released before a 
dash is complete a positive voltage is still 
applied to K. through CR3 which makes 
the dash self completing. 

The operation of the gate SN7360 is as 
follows: If either and /or both inputs are 
zero the gate has an output, If both inputs 
are positive the output is zero. 

Information about the integrated circuits 
used in the keyer is available from Texas 
Instruments, P.O. Box 5012, Dallas 22, 
Texas. Request bulletin No, DL-S 657650, 
July 1965. 



Construction 

The authors keyer is constructed on a 
Vera printed board, however, for one who 
does not have an integrated circuit soldering 
iron the TI Mech-Pac connectors are ideaL 
Wiring is not critical and phono wire or 
#30 to #32 hookup wire is recommended. 

The positive 3 volts for the integrated 
circuits is grounded to prevent floating the 
common of the key. CI and C2 shunt any 
rf to ground. Shielded lead should be used 
to minimize rf pickup. The battery drain is 
30 mA key up and 50 mA key down. A 9 
and power obtained from transmitter or 
receiver R+. 

volt zener may be substituted for the battery 

. . . W5FQA 



CiOCK 
PULSE 



KEY 
O* 

O 

n 

GATE 

OUTPUT 



I I I I I I I I I I I I 



|00T| 



[DASH (KEY DOWN! 



JGASH(KgY UP) 



O 














Fig. 2. Logic diagram of the keyer. 



MARCH 1967 



51 



J. L Elkhorne 

3009 Westknolls Lane 

Cincinnati, Ohio 4521 [ 



Edison— The Fabulous Drone 



Was Edison really the great genius schoo!books tell us 
he was? Or was he simply very diligent and hardworking? 



The Great Man confided that he tried 
everything* while working on inventions. 
When 10,000 experiments with a storage 
bait went down to failure, he said: "I 
have not failed, I have just found 10,000 
ways that won't work." 

He argued with Nikola Tesla, the brilli- 
ant Serbian engineer and scientist, telling 
him that AG electricity was a "waste of 
effort and money". 

"Looks like a bunch of Chinese laundry 
markings," he remarked of his hired mathe- 
maticians" worksheets. 

He said: "Genius is one per cent inspira- 
tion and 99 per cent perspiration." 

Most people think Thomas Alva Edison 
was perhaps the world's greatest inventor. 
But in comparison to his contemporaries, 
he was an inveterate fiddler, who scorned 
abstract work to tinker about with one 
failure after another. 

Tesla observed Edison work methods thus: 
*lf Edison had a needle to find in a hay- 
stack, he would proceed at once with the 
diligence of the bee to examine straw after 
straw until he found the object of his search*" 
Tesla said further: '1 was a sorry witness 
of such doings, knowing that a little theory 
and calculation would have saved him ninety 
per cent of his labour/* 

Edison plodded along, content to improve 
on existing ideas, insistent on hand work 
over brain work, and often completely blind 
to the uses of his own great and original 



work. Of his first phonograph, he said: 

"Mavbe we could use it for some sort of 

- 

telephone repeater," 

In later years he said of its first success- 
ful test: 'T was never so taken aback in all 
my life. Everybody was astonished. / was 
always afraid of things that worked the 
first time" 

Even after patent rights were issued to 
manufactin Edison claimed it was "just 

a fad, and would be completely forgotten 
in five years". As late as 1925 he would 
not concede that electronic phonographs 
were superior and maintained that T. A, Edi- 
son, Inc. would make an improved mechan- 
ical phonograph for long playing records. 

Also in 1925 he noted that the 'radio 
craze* would soon pass, "The present radio 
... is certainly a lemon. It will in time 
cure the dealer of any desire to handle any 
kind of radio." He also insisted that the 
public would not stand still for having to 
listen to the programming the broadcasters 
provided. 

In 1926, though very hard of hearing, 
Edison tested an electronic phonograph per- 
fected by Bertil Hauffman, a Swedish engi- 
neer, at the Edison Laboratory, Edison found 
the reproduction 'distorted and terrible* and 
ordered that Hauffman be fired. Son Theo- 
dore, director of the works, arranged for 
Hauffman to work hence in a part of the 
laboratory that Edison was not likely to visit, 

Edison once said that he enjoyed Ms deal- 



52 



73 MAGAZINE 



ness because it permitted him to concen- 
trate. Though his progressive deafness made 
him almost stone deaf in elder years, one 
wonders if the affliction also allowed him 
to ignore criticism in earlier times. 

Another facet of the Edison myth is the 
famous story of his sleeping only four hours 
a night. John J. O'Neill reports in his bi- 
ography of Tesla: "It was a regular prac- 
tice with Edison to sit down in his labora- 
tory and doze off into a three-hour nap 
about twice a day." 

Edison was strangely adverse to theoretical 
work himself; as a thinker ? he was second 
rate— as an administrator, second to none. 
The "Wizard of Menlo Park* hired batteries 
of mathematicians and physicists, laughed 
at their theoretical approach, but utilised 
their results. 

When the young genius Nikola Tesla 
came to this country, he had a letter of 
introduction to Thomas Edison, four cents 
in his pockets , and the key to alternating 
current electricity— today's how sepower— 
locked in his mind. Edison offered him a 
meagre eighteen dollars a week, providing 
he never spoke of AC. 

Tesla proved himself an able engineer 
and inventor, regularly submitting improve- 
ments for Edison equipment. When Tesla 
suggested research toward improved dyna- 
mo manufacture, Edison told him: "There's 
fifty thousand dollars for you in it— if it 
works/' Inside the week, Tesla presented 
the design. When he finally had to ask 
about the money, Edison grinned and said: 
"I guess you fust don't understand our 
Yankee humor." 

Tesla quit. Some months later, he had 
interested investors in his ideas for AC, con- 
structed working models, and applied for 
a patent. The U.S. Patent Office responded 
that the ideas contained in the original 
patent application were so far-reaching 
that no less than forty would cover them! 

George Westinghouse, industrialist and 
inventor himself, offered Tesla one million 
dollars for the rights and the Westinghouse 
Electric Company was formed. This was 
prologue to the bigtr< st battle of the 19th 
century: a technological war in which 
Thomas Alva Edison was the prime an- 
tagonist- 
Edison had recently spent $2 million with 
his DC system in New York City. The fi- 
nancial threat posed by Westinghouse and 
Tesla could not be ignored. Although Edison 



had said AC was "a waste of effort and 
money", he found his system impractical 
to produce voltages higher than 220, as 
the dynamo commutators heated badly. Too, 
line losses necessitated either large, expen- 
sive conductors or power stations spaced 
every mile or so. 

DC power left the generating plant at 
about 120 volts; the users closest to the 
plant had the brightest lights, sometimes 
so much so that bulbs burned out frequently. 
Perversely, those at the end of the line 
had light hardly better than candlepower, 
because of the voltage drop along the line. 
With Tesla*s AC system* alternating cur- 
rent could be transmitted equally to home 
or factory, with negligible power loss in 
the lines* 

Edison wrote: "Just as certain as death 
Westinghouse will kill a customer within 
six months after he puts in a system of 
any size * . * it will never be free from 
danger/* 

Westinghouse argued that of thirty deaths 
by electricity in 'recent' years, sixteen were 
from *safe* DC circuits, and none from 
Westinghouse equipment. During one period 
Edison lost about a workman a month with 
safe direct current and almost burned down 
the fashionable Vanderbilt home on Fifth 
Ave, A fire started when metallic-threaded 
draperies shorted out the wiring which had 
been placed behind it, Mrs. Vanderbilt re- 
turned home to find a confusion of fire- 
men, assistants and Edison himself- Learn- 
ing that there was a generating plant in 
her cellar* she became 'hysterical* and de- 
clared she could not live over a boiler, "We 
had to take the whole thing out/* Edison 
ruefully remarked. 

To sway public opinion in the "battle of 
the currents", Edison and Charles Batchellor 
—ironically the man who gave Tesla the 
letter of introduction to Edison— demon- 
strated the horrible dangers of alternating 
currents by electrocuting cats and dogs, 
using a one kilovolt generator. They paid 
eager schoolboys twenty -five cents a head 
for all the animals they could deliver. It 
is said that the house pet population around 
West Orange stood in danger of being 
annihilated. During one of these edifying 
illustrations for guests, Batchellor lost his 
hold on the dog he was about to electrify 
and himself received the shock. As he put 
it later: "The sensation was of an immense 
rough file thrust through the quivering 



MARCH 1967 



53 



fibers of the body/* 

After this, Edison published an article 
saying in part: "I have not failed to seek 
practical demonstration ... I have taken 
life— not human life— in the belief that the 
end justifies the means," Yet in the final 
battle of this strange war, Edison seemingly 
reversed his opinions and requested per- 
mission to install AC equipment in upstate 
New York; Westinghouse hastily agreed. 

It might be said that the news of the 
installation came as a shock to Westing- 
I muse— it was the first electric chair. The 
New York State Legislature had adopted 
a statute in 1888 to provide for capital 
punishment by electrocution. H. P. Brown, 
a former research expert for Edison, super- 
vised the installation of the 'hot squat* for 
the Edison General Electric Company* 

On August 6, 1890, convicted murderer 
William Kemmler was to be executed. The 
first attempt at deatli by legal electrocution 
was a failure, as the electric force was too 
weak* The unfortunate man was led away. 
After quick modification to the chair, "the 
miserable work was perforce done again, 
resulting in a spectacle much worse than 
hanging/* 

A frantic Westinghouse recouped by ob- 
taining the contract to provide power for 
the Columbian Exposition of 1893. Tesla had 
his own exhibit there, where he mystified 
fair goers with his scientific marvels. The 
climax of the many performances was the 
passing of one million volts of AC through 
his body to melt a copper plate. It was not 
high voltage that killed, he maintained, but 
the destructive heating effect of high cur- 
rents. High amperage DC could and did kill 
as readily as AC. While working up his 
demonstrations, he discovered the medical 
principle of diathermy. 

The public was won over to AC and in 
1895, Tesla harnessed Niagara Falls. His 
powerhouse was completed, providing AC 
for Buffalo, twenty-two miles away. It was 
hailed as the greatest engineering achieve- 
ment in the world to that date. 

In 1896, a mysterious cigar-shaped air- 
ship was seen by hundreds of people over 
San Francisco Bay, and subsequently was 
reported in successive eastward sightings. 
A New York Herald reporter obtained this 
statement from Edison, who disclaimed any 
knowledge of the never-identified craft: "I 
perfer to devote my time to objects of com- 
mercial value. At best airships would only 



be toys," A few years later, he was con- 
gratulating Alberto Santos-Dumont for in- 
venting powered flight, not recognising the 
achievement of the Wright brothers. 

The Edison Effect— the expulsion of par- 
ticles from a heated filament— grew from 
experiments with the light bulb, Edison 
found that bulb life was shortened by the 
deposit of carbon from the filament , He 
sketched in his notebook the first two-ele- 
ment vacuum tube as a solution to the prob- 
lem, having found that current would flow 
into the second element. This forerunner of 
today *& diode was patented but never used, 
and the patent lapsed, 

With the diode, his discovery of the 
Vihcric force' and a subsequent patent of 
wireless transmission based on electrostatic 
induction, he had in his grasp the elements 
of a complete radio system several years 
before Hertz demontrated the existence of 
rad.o waves. Later in life, he said that it 
was a pity he had not seen any connection 
between them, 

His first major invention, the carbon but 
ton microphone, is virtually the same today; 
it was a symbol of much of his work, since 
it improved an existing idea, the Bell device. 
Edison came, as it were, into a technologi- 
cal vacuum, purifying existing and imper- 
fect concepts, and applying much of the ran- 
dom electrical science accumulated over fifty 
years. He did enough that he could well say 
in later years his productivity brought him 
"awards by the quart" He patented over 
1,100 inventions and gained a vast reputa- 
tion while his more brilliant and less under- 
stood contemporaries arc all but forgotten. 

George Westinghouse himself patented 
over 400 inventions in his lifetime and 
founded 60 companies. 

Charles Proteus Steinmetz, whom Edison 
liked "because he never spoke of mathema- 
tics to me", published the law of hysteresis 
when he was only 27, went on to produce 
artificial lightning and delve into higher 
mysteries. He is little known today, 

Nikola Tesla, besides giving the world AC, 
demonstrated radio control before the turn 
of the century, developed a working system 
of broadcast power, lighted his laboratories 
with wireless fluorescent lights in 1889, and 
had over 700 patents to his credit when 
he died in 1943, Yet he is the forgotten 
man of electrical science. 

Edison, the Great Man, reigns supreme, 
. , . Elkhorne 



54 



73 MAGAZINE 






SPRING UP 



to a new 






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NAME 



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Address _ 

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MARCH (967 



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-r 



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r 


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Photos by Jim Harvey, WA6IAK. 



Jim Rsk WIDTY 
RFD I, Box 138 
Rindge, N.H. 03461 



A Sensitive RF Voltmeter 



One of the handiest test instruments 
around the ham shack is the rf probe or rf 
voltmeter. This almost iiidispensible unit 
may be used for neutralizing transmitters, 
tuning up oscillators and in many other gen- 
eral tasks around the shop. Most hams simply 
purchase an if probe to go along with their 
VTVM, but these probes are usualK limited 
to an upper frequency range of somewhere 
around 250 MHz. Another serious limitation 
of the familiar VTVM rf probe is that the 
lowest voltage range on the V V\ li is typ- 
ically 1.5 volts, dome of the la lest ., o<iel; 
have voltage ranges down to 0.5 yd W hill 
scale, but the vast majority are art that 



sensitive, When working with transistor rf 
stages, the millivolts (thousandths of a volt) 
become very important, and a more sensitive 
rf voltmeter than the common household 
VTVM must be used. 

There are several approaches to this prob- 
lem, but most of them are not very simple. 
The commercial instruments that read one 
millivolt full scale or less are quite com- 
plicated; they rectify the rf, chop it up at 
1000 Hz, feed it into a very high gain, nar- 
row passband ac amplifier, rectify it at the 
higher level and drive a meter movement. 
This is a very effect approach, but instru- 
ments using it cost upwards of $500, The rf 



5* 



73 MAGAZINE 



KLIPZON MINt-PROD 
iGC TYPE 33-138} 




CIGAR TUflE 



5/(6" OQ BflASS TUBE 




5/8*00 BRASS TUBE 



3/8" PHENOLIC TUBE 



//J///J////I/J////// 



1000 



rtffiill/flfiflf/fll 



ZOOOpf STANOOFF 
BUTTON CAPACITOR 




iOOOpf BUTTON 



FEEOTWRU CAPACITOR 

12 PLACES) 



GROUND CONNECT©* 



Fig, I, Cutaway view of the sensitive rf probe. Note that the cigar tube construction results in an essen 
tially coaxial structure; this type of construction ensure* relatively flat response up to 500 MHz. 






voltmeter I will describe here is not nearly 
sensitive enough to read 1 millivolt full scale, 
but with care in construction, you can 
readily detect 30 or 40 millivolt signals at 
500 MHz. This is about 15 times more sen- 
sitive than the most sensitive VTVM and 
about 50 times more sensitive than the aver- 
age one. Higher sensitivities are obtainable, 
but noise becomes the limiting factor with 
the simple construction described here, 

With this rf probe, response is relatively 
flat from about 50 MHz all the way up to 
500 MHz* The secret to this unit's wide 
frequency range lies almost exclusively with 
its layout and construction. First of all, the 
probe itself is essentially coaxial in nature, 
with the filter components mounted in a 
brass tube. To maintain leakage at an ab- 
solute minimum and to minimize series in- 
ductance, button mica capacitors are used 
in conjunction with a coaxial input. The re- 
sult is a probe that will quite accurately 
measure small levels of rf voltage up tu 
about 500 MHz. Above 500 MHz you can 
still get meter deflections with small rf volt- 
ages, but the response gradually falls off. 
This frequency roll off is a result of the para- 
sitic and leakage elements that start to take 
effect at these higher frequencies. Above 
^00 MHz for example, it is difficult to pre- 
dict the dielectric characteristics of molded 
carbon resistors. In some cases there is suf- 
ficient leakage between the two leads of the 
resistor to completely nullify the resistance. 

In addition to the compact and coaxial 
nature of this probe, the low value of load 
resistance. 270 ohms, tends to maintain an 
input-output characteristic which is almost 
completely independent of Frequency I mm 
several MHz up to 500 MHz. With the com- 
ponent values shown in the schematic, the 



response gradually falls off below 50 MHz:; 
at the expense of flat UHF response, the 
capacitors may be increased for response in 
the 3 to 30 MHz region. For the high fre- 
quency range the input coupling capacitor 
should have a value of about 500 pF and 
the filter capacitors should be 2000 pF. For 
lower frequency use of course, it is not nec- 
essary to maintain the coaxial structure of 
the probe nor to use the more costly button 
capacitors, 

The selection of a diode depends on the 
frequency range desired. Up to about 100 
MHz, almost any germanium diode will work 
quite well; the 1N34A is an excellent choice 
for this range. For higher frequencies how- 
ever, manv diodes are constructed in such 
as way that they exhibit high values of 
series inductance and leakage capacitance. 
For this reason, the familiar 1N21 and IN23 
microwave mixer diodes represent excellent 
choices for a voltmeter of this type which 
is designed for VHF use. The 1N82A is an- 
other diode that work?; quite well up to 1000 
MHz or so. Each of these diodes exhibits 
different characteristics and even diodes of 
the same type are not exactly identical. 

It is a pretty well known fact that all 
semiconductor diodes exhibit a square law 



KXJ pf 

—Hf- 

iNrtJT 



0*00^ 



w 



/77 



e7o 



1000 



/T7 



rrr 



IK 

-vw 



rooo; 







OUTPUT 



rrr 



/T7 



Fg« 2. The sensitive rf probe, For UHF use the 
f ipacitors should all be button types to minimize 
series inductance; for the tower frequencies, con- 
ventional types will suffice. 



MARCH 1967 



57 



10 

1 

7 

g 

3 
4 



m 15 



* 07 
0-6 
0.5 

0* 
03 



02 



1 















































































J 
















/ 


















































































































































































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K? 



20 BO 40 50 60 70 60 

MILLIVOLTS lftM5) 



100 



Fig. 3* The microampere per volt characteristic of 
a IN34A diode in the square law region. Above 
100 millivolts or so, this curve becomes linear. 

input-output characteristic up to several 
hundred millivolts, With germanium diodes 
the square law region is from zero to about 
100 or 200 millivolts; silicon diodes are 
slightly higher, to 600 or 700 millivolts- The 
1N34A diode for example exhibits a sensi- 
tivity of 700 to 1200 microamperes per volt 
squared in this region; a typical 1N34A 
fik/V curve is plotted in Fig. 3. It should 
be pointed out that this curve varies with 
temperature, the amount again depending 
upon the individual diode used. However, 
in amateur applications this is usually not 
a problem because the probe will normally 
be used at room temperature. Above the 
square law region the sensitivity of semi- 
conductor diodes is essentially linear and 
typically on the order of 5 milliamperes per 
volt. 

Because of the large variance between 
diodes, the rf probe must be calibrated 
against a known source for maximum ac- 
curacy. Because of the construction of this 
probe, the calibration sounds much more 
complicated that it actually is. Since the 
probe is essentially flat up to 500 MHz, it 
may be calibrated at 100 MHz or so; most 
VTVM's are accurate enough at this fre- 
quency for calibration purposes. All you 
have to do is set the output of your signal 



generator for 1 volt on the VTVM, For best 
results your generator should be operating 
on a fundamental and relatively free of har- 
monics. Since 1 volt is within the linear range 
of the diode in the VTVM rf probe, it 
should be reasonably accurate. Now all you 
have to do is connect an attenuator between 
the one volt source* You can breadboard 
an attenuator circuit for this purpose, or use 
a switchable attenuator such as that de- 
scribed bv WB6AIG and WA6RDZ1. When 
the input-output characteristics are plotted 
on graph paper, you should end up with 
something like the curve of Fig, 3. 

Construction of the probe is quite simple 
and is based upon the use of an aluminum 
cigar tube, the kind those 50c cigars come 
in. If you cant get one of these or don't 
smoke, an old pen light or piece of alumi- 
num tubing will work with a little modifica- 
tion. The tip of the probe is made up from 
a Klipzon Mini-prod (General Cement 33- 
138) and a piece of Me inch brass tubing 
from the hobby shop. This tubing is popular 
with slot car enthusiasts, so it shouldn't pose 
any procurement problems, One end of the 
mini-prod has a sharp tip with a small clip 
that may be clipped unto wires; the other 
end accepts a pin plug. 

Apply a little epoxy cement to the mini- 
prod and push it into the brass tubing. The 
mini-prod fits snugly in the tuning and is 
held firmly in place by the cement. Now 
place a Mo rubber gromment around the 
tube and push it about half way down; 
cement it in place with epoxy* 

While the epoxy is setting, take a 100 pF 
standoff button mica capacitor and solder 
it to a pin jack; this will eventually fit into 
the end of the mini-prod when the probe 
is complete. Cut a piece of % inch brass 
tubing about an inch and a half long and 
solder two button capacitors and a 1000 
ohm resistor inside as shown in Fig, 1, This 
"filter" assembly should slide easily into the 
cigar tube. Also drill a Me inch hole in the 
end of the cigar tube for the mini-prod as- 
sembly. 

Install the diode and a 270 ohm resistor 
as shown in Fig. 1, using the very shortest 
leads possible. The cathode of the diode goes 
to the center pin on C2; the 270 ohm resis- 
tor is soldered to the brass tube. On the other 
end of the tube connect a length of cable; 
this lead will be connected to the microam- 
meter. Install the complete assembly (mini- 
prod, CI, CR1, Rl and the filter) into the 



58 



73 MAGAZINE 



iuMi4iiiniiitni in iim [in tn i ii uiMMinMiiMiiitiiuiiiiiMiiiiinirii7iiMiimminiii limit u i »n > m u ^ i miik iem m tn Mitfii i nut inin nnn mimii in tin tin linn 1111 iirn i i iinii ten iiiitinittiirMiMimi n^in k;_i 



73 BOOKS FOR YOU 



5 



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This thick (112 page) book 
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INDEX TO SURPLUS 

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INDEX TO 



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The VHF Antenna Handbook 
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it's a complete collection of 
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$2 

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The Care and Feeding of a 
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HAM TELEVISION 

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Books shipped prepaid in US and Canada. 

73 Magazine 

Peterborough, N. H. 03458 



uiu.iiitiiiiiiiiiiiMiMiiiiiiiiiiimimminiMiniiiimriiii!iuniinMiMiiinMinimi!ini«i iiniii iiiiiiiiiiiiiiitiiliiiiiliriiiiiiiimiiiiiiiiiifMlimilliriinillinilllltiiiMIIHIIIIIirilllllHUItllHiiiitiiill imil 




Disassembled rf probe. The Klipion Mini-prod is 
on the left, the button coupling capacitor, diode 
and 270 ohm resistor to the right, followed by the 

filter and phenolic tube* The cigar tube housing is 
in the background. 

cigar tube unci cut a length of % inch phen- 
olic tubing so that it protrudes about Vs inch 
from the end of the cigar tube, When the 
cover is in place this tube will compress the 
unit together and ensure a physically strong 
assembly. The shielded lead is brought out 
through a small rubber grummet mounted in 
the cover. 

In addition to the rf probe, you will need 
a very sensitive microammeter for measur- 
ing small levels of rf. Occasionally 10 or 20 
microampere movements are available at 
bargain basement prices, but usually an- 
other approach is necessary; the sensitive 
microammeter illustrated in Fig. 4 is a good 
example, This meter uses a high gain tran- 
sistor meter amplifier to obtain full scale 



readings down to 10 microamperes full scale 
on a 1 milliampere meter. With a full scale 
calibration of 10 microamps, it is quite easy 
to read a half microamp or so; this corre- 
sponds to 28 millivolts peak to peak with 
my probe. 

The sensitive microammeter illustrated 
schematically in Fig. 4 consists of a current 
amplifier with the 1 mA meter in a bridge 
circuit 2 . This circuit is quite stable with tem- 
perature and slight variations in supply volt- 
age may be compensated by the zero con- 
trol on the front panel. Almost an) high 
gain transistor will work in this circuit, but 
silicon is preferred because of its better 
leakage characteristics. The only other re- 
quirement is that the transistor must main- 
tain linear current gain and high beta at 
low collector current levels; the 2N3392 is 
inexpensive and works very well 

With the switch in the 10 microampere 
position, the 10k gain control is adjusted to 
provide 10 microamperes full scale. With a 
1 milliampere movement, this et rrcsponds 
to a current gain of 100, For full scale read- 
ings of 50 to 200 microamperes, meter 
shunts are proved for 5 and 20 mA full 
scale with the 1 mA movement; the transis- 
tor amplifier will maintain a current gain 
of 100. For meter readings of 1 milliampere, 
the transistor amplifier is disabled and the 
meter is operated in the normal manner. The 
value of the shunts may be calculated by 
using the formula found in any of the hand- 
books. 




2N5392 



6AI* 



AVV — *■ 



ion 




SIB 



; 5f 



*S2 
O ^ /^f 



t 



1 









SIC 



—J_ . 



ZERO 



SID 




OFF 



© pa 



50F« 



ZOO ua 

I 
l 

lOOQf* 



SI - 4 POLE, 5 posmoN 

ROTARY SWITCH 
(MALLORT I3ML1 

FOR VALUES OF SHJtfT 
RESISTORS R^ AW Rj^ 
SEE TEKT, 



EMITTER 




2N3392 

BOTTOM VIEW 



Fig. 4. Transistorized microammeter. This instrument will provide full scale readings down to 10 /aA. Al- 
though a 2N3392 was used here, any high gain silicon transistor that maintains high current gain at low 
collector current levels Is suitable. 



60 



73 MAGAZINE 



In my transistorized niicroammeter 1 
mounted the transistor amplifier circuitry 
and meter shunts on a phenolic strip con- 
nected to the meter terminals. The gain 
potentiometer is also mounted on this strip. 
With a circuit as sensitive as this, noise can 
be a very serious problem if the circuit is 
not properly shielded- In this case a small 
coaxial cable was used in the input and the 
amplifier and meter were built into a metal 
box. In addition, the input was bypassed 
with a 0,01 mF disc capacitor. 

With the sensitive microam meter and cali- 
brated probe, it is quite easy to accurately 
measure rf voltage down to 30 or 40 milli- 
volts. However, since this is a peak respond- 
ing instrument, you have to be a little care- 
ful or you will obtain some very optimistic 
readings. If there is any harmonic content 
in the waveform you are reading, it is apt 
to be quite a bit higher than predicted, and 
the rms value will not be 0.707 of the peak 
reading; the 0.707 value applies only when 
the waveform is sinusoidal. This is not us- 
ually the case with rf oscillators and am- 
plifiers, but if the harmonics are suppressed 
with high Q tuned circuits, the error will 

be negligible. 

In addition to measuring actual rf volt- 
ages, this probe has several other uses. It 
be used as a very sensitive untuned 
strength meter by simply clipping a 
length of wire to the tip; in some 
cases where the rf field is strong and the 
probe can be placed close enough to the 
transmitter, this may not be necessary. 
Hence another precaution: don't use the 
probe in strong rf fields when measuring 
small rf voltages; the rf field \ "11 negate 
the voltage reading. This probe may also 
be used as a demodulator for a VHF sweep 
generator. Just connect the probe to the 
circuit being swept and connect the output 
to your oscilloscope. It may also be used to 
measure the SWR along a piece of open 
wire transmission line (or twin lead). When 
the probe is brought in close proximity to 
the transmission line, it will provide an up- 
scale reading on the microam meter. The 
ratio between peaks and valleys as the probe 
is moved along the line is the voltage stand- 
ing wave ratio. 

In some measurements you may find that 
the probe will load down low-capacitance 
high-Q circuits. If you are only interested 
in peaking the circuit, and many times this 
is the case, this effect may be minimized 



may 

field 




• 









Inside of the meter amplifier* The transistor and 
gain calibration control are mounted on a piece 
of bateli+e attached to the meter terminals. 
The rf probe disassembled. See Fig. L 

by connecting a resistor in series with the 
probe. The Klipzon Mini-prod is ideal for 
this purpose because it will securely hold 
one lead of the resistor; the other lead may 
be used for probing. If a 5000 ohm resistor 
is used, it represents less than one pF coupl- 
ing above 30 MHz; this should eliminate 
any detuning effect of the probe. 

There are many other uses for the sen- 
sitive rf probe, limited primarily by the in- 
genuity of the user* But in it main applica- 
tion, that of measuring very small rf volt- 
ages, it is unbeatable for its expense and 
complexity. Although high rf voltages or 
mechanical shock may cause permanent 
damage to the diode, my probe has proven 
to be particularly resistant to burnout and 
lias accepted peak surges of 500 Vdc and 120 
Vac with no apparent effect on calibration. 

. . . W1DTY 



1. "Low Power Attenuators for the Amateur 
Bands," WB6AIG and WA6RDZ, 73 Magazine, 
January 1967. 

2, "Transistor Meter Amplifiers," WAGHSO, 73 
Magazine, January 1966. 



MARCH 1967 



61 



Tom Lally KIUBA 
28 Amory Rd. 
Waltham, Mass* 



SDRAWKCAB Power Supply 



Articles have already been written about 
building kW supplies with TV power trans- 
formers, using voltage doubling and series 
capacitors. The solid state man, shunning 
the lethal voltage approach to rf power gen- 
eration, looks for a way to lower the line 
voltage. With this in mind, and with a junked 
TV in the shack, the supply shown here 
evolved. With 115 V in, the outputs are as 
follows: 

Unregulated 16, El, 32, 41 Volts 

Regulated 12, 24 Volts 

The transformer is hooked up with the 
secondary connected to the line, and the 
primary as the input to a bridge and filter. 
Four levels of voltage are available at the 
unregulated output, which is the next best 
thing to owning a Variac. With a little more 
s witchcraft, and with more filament wind- 
ings, more levels can be had. The HV wind- 
ing center tap provides a choice of high or 
low outputs, while the filament windings 
give series aiding or opposing differential 
adjustment at either level, Stud silicon 
diodes are used in the bridge. The .008 F 
capacitor is probably a little fat for the ap- 
plication, and a mere 4,000 juF would still 
guarantee a T9 report on the air. 

The regulated outputs are at the 12 and 
24 volt levels for this supply, but depending 
on your transformer, or your oscillator re- 
quirements, these could be modified to 9 
and 18 volts, or even lower. For the loads 
presented by solid state receivers, the stud 



XV XFMR 




HU WftONG 



SI * OPOT. CENTER OFF 



Here's KlUBA's transistor power supply. 



zener is an adequate regulator, so no series 
type regulation had been built in. On trans- 
mit, a voltage "droop" of over 25^ has 
gone unnoticed on the air, as has a ripple 
considerably higher than the 0.1 V of this 
supply. Accordingly, no attempt has been 
made to regulate anything but the oscillator 
supply* If too much current is drawn from 
the unregulated output, however, regulation 
cannot be maintained. 

Important criteria for selecting the trans- 
former are: 

1* The turns ratio 

2. The internal resistance of the wind 
ings 

3. The number of filament windings. 
Transformers which give the highest volt- 
age when normally connected are not nec- 
essarily what you want for this supply, since 
they may give too low an output when con- 
nected backwards* Also, their HV windings 
may exhibit high resistance which reduces 
the stiffness of the dc output. The author's 
supply has an internal resistance of 8 ohms, 
which limits maximum output to 53 watts. 
More filament windings mean greater range 
of differential adjustment. 

The aluminum chassis acts as a heat sink 
for the bridge and zener diodes. All diodes 
are isolated from chassis ground with mica 
washers to allow a choice of positive or nega- 
tive grounding. Threaded 6-32 stock holds 
down the capacitor, but it could have been 
epoxied to the chassis. The AC line switch 
is DPDT with center off position to minimize 
the number of controls, and it also cuts in 
the second zener when in the "HIGH" po- 
sition. The pilot light is visibly dimmer in 
the "LOW" position, but it can still be seen. 
Grommets protect the transformer leads 
and the capacitor lugs. 

On low voltage, a direct short will not 
blow the 3£ Amp fuse, but component dis- 
sipations are within safe limits. The trans- 
former is not operated anywhere near its 
allowable power limit for step-up operation, 
but it exhibits less than 10 °C rise at full 
load, and should be adequate until the ad- 
vent of the solid state kW, 

KIUBA 



« ■ 



62 



73 MAGAZINE 



6W wi^ *a£ Vrfkt 




We believe the 

new 2K-2 is 

the finest linear 
amplifier ever 
made for the 
amateur service 




2K-2 FLOOR CONSOLE $675.00 



The new 2K-2, Floor Console, 2KD-2 Desk Model and 2KR-2 RF Deck are destined for 
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signal sharpness, remarkable power output and modern design all combine to make 
the 2K-2 the finest linear available to the amateur today. 

Wouldn't you like to own the finest? Write today for full information. Note to commer- 
cial and military users: please ask about the new 4-K high power linear. 

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within 90 days for full credit toward the purchase of NEW equipment. Write for bulletin. 

TED HENRY (W6UOU) BOB HENRY (WOARA) WALT HENRY (W6NRV) 




CALL DIRECT 



• < 



USE AREA CODE 



Butler 1, Missouri, 64730 
11240 W. Olympic. Los Angeles, Calif., 90064 
931 N. Euclid, Anaheim, Calif., 92801 
6116 N. 27th Ave.. Phoenix, Ariz., 85017 



816 679-3127 

213 477-6701 

714 772-9200 

602 AM 4-3895 



East Coast Rep,: Howard Laughrey, 2 Elizabeth St.. Chappaqua, N.Y. 1 0514, (914) CE 8-3683 

"Worlds Largest Distributors of Short Wave Receivers" 



James Forney WB2CCM 
New Canaan, Conn. 



A Panadapter Converter 



Having trouble getting those pretty pictures with your panadapter? May- 
be you need an isolating amplifier. 



I recently got a panadaptei It worked 
fine with a signal generator, but gave pretty 
dismal results when I connected it to my 
receiver, 

A careful search through the literature 
turned up all sorts of interesting notions on 
how to connect a panadapter to a receiver. 
Each was tried without success. Some loaded 
the mixei too much. Others attenuated the 
signal too much. Finally a reasonable pre- 
sentation came on the screen, but only after 
reducing the length of RG-58/U connecting 
the adapter to the receiver to a ridiculous 
length that left the panadapter back to back 
with the receiver. 

Something had to be done. A cathode 
follower was the obvious approach. One was 
installed as close as possible to the mixer 
stage. This gave a very high impedance to 
the mixer stage, but a low impedance into 
the coax running to the panadapter input. 
The results were excellent. 

Since most receivers have an accessory 
socket on the back, this seemed to be an 
ideal way to get the B4- and filament volt- 
age, and at the same time provide a mount- 
ing for the cathode follower circuit. The 




R350A) 




RCVR 

MIXER 




.05 p 1 

TO PAN- 
A&APTtR INPUT 



ftG58/lJ 



A simple panadapter converter. 



origonal unit was constructed in a Mini-box 
1% x 2Vs x 2%, using the piece that has 
the two ends on it for the chassis. 

An octal plug is mounted on the long 
side. This not only makes the necessary elec- 
trical connections but also holds the assem- 
bly in place on the back of the receiver. 
The cathode follower circuit is assembled on 
one end, and an octal socket is mounted in 
the other end in case any additional acces- 
sory is to be connected to the receiver. 

A 6AB4 tube was used because it was 
handy, but any of a number of other tubes 
might be substituted with only minor 
changes in the circuit. A more compact unit 
could probably be built easily by using a 
triode Nuvistor* Construction is straightfor- 
ward but lead lengths should be kept to a 
minimum, and the length of RG58/U be- 
tween the mixer and the cathode follower 
should be kept as short as possible to mini- 
mize attenuation. The 47 k resistor should 
be as close to the plate connection as pos- 
sible, and likewise the 50 pF capacitor as 
close to the 6AB4 grid as possible. The 100 
ohm resistor in the plate circuit of the 6AB4 
provides decoupling and was adequate in 
this installation, but a different value might 
be required in other installations. 

Using this unit between the receiver and 
the panadapter, no detuning of the mixer 
is noted when connecting to it, and enough 
coax to allow the panadapter to be removed 
to a respectable distance from the receiver 
has little effect on the input signal. In fact 
despite the fact that the gain of a cathode 
follower is of necessity less than L, the 
lowered impedance gives the effect of an 
actual gain. 

WB2CCM 



» # 



64 



73 MAGAZINE 



Jim Fisk WIDTY 
RFD I, Box 138 
Rmdge, N.H. 03461 



73 Useful Transistor Circuits 



Useful transistor circuits for audio and speech equipment, re 
ceivers, transmitters and test equipment. 



Circuits for Audio Equipment 



Direct coupled amplifiers 

The direct coupled amplifier illustrated 
in Fig* 1 is just about as simple as possible, 
but provides very usable results. The col- 
lectors of the first two transistors operate 
at about 0,3 volts; this type of operation 
yields somewhat less than normal gain, but 
provides considerable reduction in noise pro- 
duced at the input by die transistor. The 
biasing of the first stage is controlled by 
resistor Rl and because of the direct cou- 
pling between stages, indirectly controls the 
bias to the other two stages. Since tlie gain 
and leakage varies widely between differ- 
ent transistors, this resistor must be adjusted 
experimentally to provide optimum bias for 
the last transistor (Q3). This is easily done 
by adjusting its value until there is 0.8 
volts across the headphones (points A and 
B in the schematic). 



PHONES 




-1,5 



Fig. I* Simple direct coupled amplifier. Transistors 
Ql, Q2 and <?3 should be the 2N207, 2N584, 
2NI09B, SK3003, GE-2 or HEP-254. 



Since Rl is connected to the collector of 
Q3, bias variations caused by changes in 
temperature are reduced by negative dc 
feedback introduced by this resistor. For 
example, as the leakage in Ql increases 
with temperature, the collector voltage on 
Q3 decreases. The increased leakage is par- 
tially compensated for because the lower 
voltage on Q3 causes less current to flow 
through RL Generally speaking, this cir- 
cuit will compensate quite nicely against 
temperature changes up to about 100 °F. 
Above 100° it is possible that the transistor 
will be driven into nonlinear operation with 
resultant distortion and reduced power out- 
put 

The dc resistance of the headphones is 
very important in this circuit because the 



OUTPUT 



rrt 




"^cntcn 1 



Fig. 2. High voltage direct coupled amplifier. The 
gain of this amplifier is equivalent to both sections 
of a I2AU7. All transistors are 2N384. SK3008. 
GE-9 or HEP-51. 



73 TRANSISTOR CIRCUITS 



IA 



-200 




Fig. 3. This simple direct coupled amplifier pro- 
vides 30 dB gain and identical 1500 ohm input 
and output impedances. For higher gain, similar 
units may be cascaded up until 10 volts peak to 
peak is obtained at the output* 

voltage drop across them determines the 
operating conditions of all three stages. For 
optimum operation , the dc resistance of 
the earphones should be in the neighbor- 
hood of 1000 ohms. Most phones with an 
impedance of 2000 ohms have a dc re- 
sistance of 1000 ohms, but if you Ye in doubt, 
the resistance may be easily measured with 
an obmmeter. 

The main advantage of the high voltage 
direct coupled amplifier in Fig. 2 is that 
it may be connected directly to a rather 
high value of B-K Its gain is equivalent 
to a single 12AU7 (both sections) and be- 
cause of the direct coupling, provides ex- 
tremely wide bandwidth. Although the in- 
put impedance of this circuit is only 2000 
ohms, it is still very useful for many ap- 
plications where a simple amplifier is re- 
quired. 

Another very simple direct coupled ampli- 
fier is illustrated in Fig. 3. This amplifier 
provides almost exactly 30 dB gain and 
has identical 1500 ohm input and output 
impedances. For extremely high gain then, 
similar units can be cascaded up until an 
output voltage of 10 volts is obtained. This 
amplifier is also quite wideband, and with 
the transistors specified, the gain is essen- 
tially flat up to about 1 MHz. 




0-4.5 



Fig. 5* This wideband amplifier exhibits 26 dB 
gain from 5 Hi to over 30 MHi and wilf deliver 
a 7 volt signal into a 100 ohm load. Transistors 
pi and Q? are 2N22IB, 



Wideband amplifiers 

In the wideband amplifier shown in Fig, 4 5 
the gain is controlled by the feedback re- 
sistor Rr„ With a 10 kilohm feedback resistor, 
the gain is greater than 30 dB from 10 
Hz to 17 MHz. When the resistor is com- 
pletely removed from the circuit, the gain 
is greater than 50 dB up to about MHz, 
but the biasing of the input transistor be- 
comes very critical to prevent signal dis- 
tortion. Note that the large electrolytic cou- 
pling capacitors should be paralleled with 
smaller capacitors that have good high fre- 
quency characteristics. 

Another wideband amplifier is illustrated 
in Fig. 5; this amplifier has a frequency 
response from 5 Hz to over 30 MHz* The 
voltage gain over this range is 26 dB and 
the amplifier will deliver an undistorted 7 
volt sine wave into a 100 ohm load. This 
circuit has excellent stability and linearity, 
and by adjusting the bias and emitter by- 
pass capacitor CI experimentally; the fre- 
quency response may be increased up to 
50 MHz. 



Fig- 4. The gain of this 
wideband amplifier may be 
controlled by the value of 
the feedback resistor R f . 
The I OK resistor shown 
here provides more than 30 
dB gain from 10 Hi to 
17 MHi, Q I and Q2 are 
2N2I88, SK3006, GE-9 or 
HEP-2, 



OUTPUT 




ifc "IOOjiF + lOOpF 



2A 



73 TRANSISTOR CIRCUITS 










+ 15 



Fig. 6. The gain of this 
amplifier is controlled by 
the nonlinear feedback pro- 
vided by two back to back 
diodes and the value of 
the feedback resistor R*. 
Ql is a 2N706, 2N708, 
2N3394 or HEP-50. 




O OUTPUT 




Gain controlled amplifiers 

It is a well known fact that the gain 
characteristics of an amplifier may be shaped 
by applying nonlinear feedback. In the ampli- 
fier of Fig, 6, the nonlinear feedback is 
furnished by two back to back diodes in 
the collector to base feedback path. When- 
ever the signal at the collector is high enough 
to forward bias the diodes (greater than ap- 
proximately 0.6 volts peak to peak), nega- 
tive feedback occurs and the gain of the 
amplifier is reduced. The gain of the stage 
may be further controlled by the value of 
the feedback resistor (Rt) as shown in the 
amplifier response curve, If it is desirable 
to have the non linearity occur at a higher 
level (greater than 0.6 volts peak to peak), 
more than one diode may be added to each 
leg of the feedback network. For lower 
levels, germanium diodes may be substituted 
for the silicon diodes specified in the sche- 
matic. With the germanium diodes in the 
feedback path, nonlinearity will occur when 
the signal is greater than about 0.1 volts 
peak to peak. 

A voltage controlled, variable gain ampli- 
fier has many applications in automatic 
volume control, amplitude modulation and 




+ 40r 



+30 





CURVE IS INDEPENDENT OF 
FREQUENCY FROM OQ H*~ 
TO I0O kHz AND BEYOND 



-10 



O 1.0 2.0 3j0 4.0 3UD 6.0 

CONTROL VOLTAGE Ec (VOLTS* 

Fig, 7. Voltage controlled amplifier uses the vary- 
ing impedance of a germanium diode in the 
emitter circuit to control gain. Transistor Ql may 
be a 2N696, 2N3564, SK30I9, GE-IO or HEP-S4. 



0,5 1,0 

INPUT ( VOLTS! 



remote gain adjustment circuits. The only 
difference between the circuit shown in 
Fig. 7 and a standard common emitter ampli- 
fier is that a IN34A diode is used in place 
of the emitter resistor. In an amplifier of 
this type, the gain of the stage is critically 
dependent upon the impedance of the emit- 
ter circuit. Since the impedance of the diode 
varies with the amount of current through 
it, the gain of the stage depends upon the 
transistor emitter current. The 1N34A was 
chosen because it provides an extremely 
wide impedance variation with a relatively 
gradual rate of change. This diode typically 
exhibits an impedance range from 15000 
ohms at low levels to 200 ohms or less with 
high currents. The slow rate of impedance 
change is required to minimize distortion. 
This circuit is useful in ALC and AGC 
circuits, feedback regulation and other cases 
where wide dynamic range and instant re* 
sponse are required. 

Preamplifiers 

The simple low cost preamplifier in Fig. 
8 provides extremely flat response from 10 



-20 O 




20 uF 



£70 



pWV-O 

BALANCED 
600 ju LINE 

i-WV-O 

At™ 
A B 

Fig. 8. High impedance preamplifier provides up 
to 1*2 megohms input impedance; the exact value 
depends upon the build-out resistor R. Both Ql 
and Q2 should be a 2N26I3, 2N26I4, 2N2953, 
SK3004, GE-2 or HEP-254, A balanced output 
for reduced hum and noise may be obtained by 
using the padded output In B, 



73 TRANSISTOR CIRCUITS 



3A 



+30 




-30 



Fig. 9. This preamplifier provides 1 1 dB gain 
from 0.5 Hz to 2 MHz and has an input impedance 
of 32 megohms. Transistors pi, Q2 and Q4 are 
2N338. SK3020 t or HEP-53; Q3 Is a 2N328, GE-2 
or HEP-52. 

Hz to 30 kHz and at the same time exhibits 
an input impedance up to 1.2 megohms. 
The input impedance of the first transistor 
with the unbypassed emitter resistor is on 
the order of 50,000 ohms; by including the 
build-out resistor R in the circuit, the input 
impedance may be increased up to 1.2 
megohms. Without R in the circuit, the 
voltage gain is approximately 15. As the 
value of R is increased, the voltage gain 
decreases and the entire circuit exhibits 
unity gain when the value of R is 1,2 
megohms. 

The output impedance of this simple pre- 
amplifier is particularly low, so it may be 
used for driving all types of circuits. Har- 



monic and intermodulation distortion are 
very low if 600 ohm circuits are connected 
across the output. It will also drive small 
8 ohm speakers, but the distortion will be 
quite a bit higher. 

The basic circuit provides an unbalanced 
output which should be suitable for most 
applications, but where hum and noise are 
a problem with balanced 600 ohm systems, 
the balanced output of Fig* 8B may be 
used. This pad adds a total of 6 dB loss 
in the output, but it does get rid of the 
hum and noise. 

The four transistor preamplifier illustrated 
in Fig. 9 exhibits an input impedance of 32 
megohms and provides 11 dB gain from 0.5 
Hz to 2 kHz. The high input impedance 
of this amplifier is a function of the two 
negative feedback loops; one from the emit- 
ter of Q2 to the collector of Ql ? the other 
from the junction of the 2.7k and 6.8k re- 
sistors in the emitter of Q4 to the emitter 
of Q2. The output impedance of this ampli- 
fier is 20 ohms so it may be used for driv- 
ing many types of circuits* 

In many cases an amplifier with an in- 
put impedance approaching that of a VTVM 
is required to keep circuit loading to a 
minimum. The amplifier of Fig. 10 more 
than meets these requirements; it provides 
up to 20 megohms input impedance, de- 
velops 1 volt rms across a 3300 ohm load 
and exhibits a frequency response from 10 
Hz to 200 kHz. 

The development of this circuit started 



-12 O 





4T0 



200 k -» 



IOjjF 



i»— aa\ -Hfr- — **i* 




(A) (B) 

Fig* 10. This high impedance preamplifier provides up to 20 megohms input impedance and has 
a frequency response from 10 Hi to 200 kHz* Circuit B was developed from circuit A by replacing 
the emitter resistor in A with Q3 and adding an emitter follower to reduce loading. The input im- 
pedance is further increased by the components shown by the dashed line. All transistors are 2N2I88, 
SK3005, ©E-9 or HEP-2. 



4A 



73 TRANSISTOR CIRCUITS 



MJOfO 
OUT 

o 




COMPRESSED 

OUTPUT 
2£OJc 



Fig, II. Microphone amplifier using a field effect 
transistor has an input impedance of 5 megohms* 
Q[ is a 2N4360, TIM 12, LM 12 or U-IIO. By re- 
versing the polarity of the supply voltage, a 
2N3820, MPF-I04 or HEP-801 may be used, 

with the circuit shown in A. Here conven- 
tional bootstrapping was used on a basic 
emitter follower circuit to eliminate the 
shunting effect of the base bias resistors. 
When a transistor with a current gain of 
100 was used, the input impedance was 
measured at 200K with a 3300 ohm load, 
A significant increase in input impedance 
may be obtained by replacing the emitter 
resistor of Ql with the collector resistance 
of Q2 as shown in B, To keep the loading 
as light as possible on the emitter of Ql, 
an emitter follower (Q3) is used, With this 
circuity the input impedance is slightly over 
1 megohm with a 3300 ohm load. 

The input impedance of this circuit may 
be further infcreased with the addition of 
the components shown by the dashed hues. 
However, if this positive feedback is over- 
done, the circuit will oscillate. If, on the 
other hand, the 200k feedback pot is care- 
fully adjusted, the input impedance may be 
raised to 20 megohms or so before instability 
occurs. 

The high impedance microphone pream- 



ble 



K)0 

rr, 




Fig. 12, Two stage clipper/preamp will increase 
the talk power of your rig. Transistors Ql and 
Ql are 2NI304, 2N2926, 2N339I, 5K30II, or 
HEP 54. The diodes are 1N456 or HEP-158. 

plifier illustrated in Fig. 11 makes use of 
the inherently high input impedance of field 
effect transistors. This impedance is raised 
still higher by the use of the 2 /*F boot- 
strap capacitor from source to gate; in this 
case to about 5 megohms. This circuit's 
output impedance of 2k is suitable for driv- 
ing other FET's or conventional junction 
transistors. 

Clipper/preamplifier 

The microphone elipper/preamp shown 
in Fig. 12 is very simple to construct and 
allows you to stay as far away from the 
mike as you like; it does a very good job 
of beefing up weak audio signals. It was 
designed primarily for high impedance dy- 
namic microphones, but may be used with 
other mikes with slightly less gain. It pro- 
vides up to 10 dB gain on low level audio 
signals and since it uses a minimum of parts> 
may be easily constructed in a small mini- 
box. 

Although the best way to adjust a clipper 
such as this is with an oscilloscope^ the 
gain control may be set so that the final 



10 



OUTPUT 
O 




+ 18 



W 






3 



X>3 











































































































































































































































































! 








































































































































































f 


> 






















1 
























f ' 
























/ 
























/ 
























/ 
























/ 

























4 S 6 7 
OUTPUT VOLTS 



a 



9 



10 ii 



12 



Fig. 13. This simple dynamic range compressor provides more than 50 dB range; 
wi+h a 20 millivolt signal but will not saturate with input voltages up to 6 or 
diodes are IN9I4; transistor Ql should be a 2N2926, 2N339I, SK30I0, GE-8 or 



it exhibits gain 
7 volts, All the 
HEP-54. 



73 TRANSISTOR CIRCUITS 



5A 



-20 V 



25 







BANDWIDTH 
I0K>-* — - 



33DK<? 47K 



/77 



Ql,0£ - 2N465, 2N295i, EK3004 

Fig. 14. This simple audio bandpass filter may be 
narrowed to the limits of unintelligibility. At a 
bandwidth of 80 Hi, it provides about 20 dB gain. 
The input is connected to the phone jack on your 
receiver while headphones are connected across 
the output, 

audio stage (of your transmitter) approaches 
saturation on a steady whistle (into a dummy 
load please) ; this will approach optimum 
adjustment, A final check should be an on 
the air report from a nearby station so 
you can determine the approximate range 
settings appropriate for your particular trans- 
mitter 

Compression amplifier 

The compession amplifier illustrated in 
Fig. 13 provides a minimum output signal 
with only 20 millivolts {0,02 volts) input, 

+ 9 V 




QI,Q£ 2N29£5, £N339I, 2N3S65 
Q3 £142712, 2N34I5, 2N356G 

BANDWIDTH 

CHOOSE L AND C FOR RESONANCE AT THE DESIRED FREQUENCY. 
FOR CENTER FREQUENCY OF IOO0 Hi, USE 250 mH AND O.I jjF 

Fig, 15* This three stage audio filter uses two 
series resonant circuits to provide a very narrow 
audio passband. The Q of the circuits, and there- 
fore the bandwidth, is controlled by the amount 
of feedback. 



but will not saturate with input voltages 
up to 6 or 7 volts. The secret to its op- 
eration of course lays in the diodes con- 
nected across the collector load resistors, 
As the signal output is increased, the diodes 
conduct one by one and lower the resistance 
of the collector load. Although this ampli- 
fier has a minimum gain of 1 and a maxi- 
mum gain of 15 with the components shown 
in the schematic, the gain characteristics 
may be made to follow other curves by 
the proper selection of load resistors and 
diodes. 

Audio filters 

The two transistor audio filter in Fig* 14 
uses positive feedback to increase the Q 
of an inexpensive LC circuit to a very high 
degree. At a bandwidth of 80 Hz for ex- 
ample, this circuit provides 20 dB gain and 
furthermore, the bandwidth may be de- 
creased to the limit of intelligibility* The 
gain stability is increased m this amplifies 
by the use of negative feedback from col- 
lector to base of Ql; this also serves to re- 
duce the output impedance and increase the 
power transfer to the succeeding stage* 

At frequencies far removed from the reso- 
nant LC circuit in the emitter of Q2, the 
emitter impedance is essentially that of the 
10k emitter resistor, As resonance how- 
ever, the low series impedance of the LC 
network predominates and increases the 
gain of the stage. Since the output signal 
is in phase with the input signal, the feed- 
back through the 10k bandwidth pot and 
330k resistor is regenerative. As the gain 
of the amplifier increases near resonance, 
the output voltage rises sharply and trans- 
forms the low Q circuit into a highly se- 
lective audio amplifier. 

The proper value for the 330k feedback 
resistor varies from transistor to transistor, 
so the value of this resistor should be chosen 
experimentally* This resistor should just 
produce oscillation when the bandwidth pot 
is advanced to the maximum feedback posi- 
tion. To use this circuit, simply plug it into 
the phone jack on your receiver, connect 
a pair of headphones across the output and 
advance the bandwidth control until a whistle 
is heard; back off a little on the band- 
width and it's ready to operate. 

The audio filter illustrated in Fig* 15 is 
somewhat similar to the one in Fig, 14 
except that the passband has a better shape 



6A 



73 TRANSISTOR CIRCUITS 



INFH.IT 



Fig, 16. This highly versa- 
tile audio filter may be 
used to completely shape 
the audio spectrum of your 
receiver or transmitter; it 
may be used with the fil- 
ters out, or with the vari- 
able low- and high-pass fil- 
ter networks connected. All 
the transistors are low cost 
audio types such as the 
2NI305, 2NI380, 2N26I3, 
GE-2 or HEP-253. 




OUTPUT 



CD 


























■H««a«i 























FILTER 


OUT 








;'' 


,.-• 


















^*s 


... 

*> 








10 


« 


** 


* 






















































^L 










1 ' 








20 






























































• ^t 
















30 


























^L 
































. 


















40 






































































' ■ 






SO 














































— .. . . 


































































1 











o 



o 



8 § 






J* 






s 



o 



FREQUENCY (H/) 



factor because two series resonant LC cir- 
cuits are used. Here again feedback is used 
to raise the Q of the resonant circuits to 
a very high value. The 47k resistor in the 
feedback line should be adjusted experi- 
mentally so that the circuit will just oscil- 
late when the 100k bandwidth pot is shorted 
out (maximum clockwise position). Although 
the LC values shown in the schematic are 
for a center frequency of approximately 
1000 Hz, other values may be used for 



300 k 




MAr 



SOOk 
TREBLE 



Fig. 17. Resistance-capacitance tone controls are 
usually not too satisfactory with junction transistors 
because of heavy loading. The high impedance 
characteristics of the FET eliminates this problem 
with no loss In the dynamic range of the tone 
control. Ql is a 2N2943, 2N3820, MPF-105 or 

HEP40L 



other center frequencies. 

One of the problems in amateur SSB com- 
munications is that the audio spectrum of 
the speech amplifier should be shaped so 
that it amplifies only those signals between 
about 300 and 3000 Hz. This can be accom- 
plished by high-Q tuned circuits, but the 
inductors required are quite large and ex- 
pensive. A simpler approach is to use the 
adjustable audio bandpass filter shown in 
Fig, 16, When the high- and low-pass filter 
of this amplifier are out of the circuit, it 
is flat within 1 dB from 100 Hz to 50 kHz. 
With the filters in the circuit, the audio 
may be shaped between the limits shown 
in Fig, 16. 

Tone control 

Audio tone controls using conventional 
junction transistors are difficult to build 
because the low input impedance of these 
devices seriously limits the tone control's 
dynamic range. An obvious solution to this 
problem lies in applying the inherently high 
input impedance of the field effect transis- 
tor. The tone control illustrated in Fig< 17 
should be familiar to old vacuum tube hands; 
it is a straightforward tone control for both 
treble and bass using a modern FET in place 
of a thermionic trioele. 



73 TRANSISTOR CIRCUITS 



7A 




O OUTPUT I 



Of 
° OUTPUT 2 



+ 20 



Fig- IS, This phase splitting circuit provides two 
out of phase signals for driving a push pull am- 
plifier without an expensive transformer The gain 
of the stage as shown is ISO, but this may be 
adjusted by changing the value of the 22 K feed- 
back resistor. Q\ and Q2 are a complimentary pair 
such as the 2N652 and 2N388 or 2N2430 and 
2N2706. 



Phase splitter 

The simple phase splitting circuit in Fig. 
18 is a two stage direct coupled amplifier 
connected as a complementary pair with 
feedback and illustrates a novel way of ob- 
taining out of phase driving signals for a 
push pull amplifier without an expensive 
transformer. The input transistor is a com- 
mon emitter voltage amplifier with its col- 
lector tied directly to the base of Q2, The 
3k resistor in the emitter of Q2 provides 
bias for this transistor but does not cause 
regeneration because it is common to both 
the base and emitter. The 13k resistor sets 
the overall circuit bias and its value is 
chosen so that the collector and emitter of 
Q2 are at the desired operating level. The 
22k feedback resistor provides negative feed- 




(00 pF 



Fig. 19. This phono preamplifier uses frequency 
selective feedback between the collector and base 
of Ql to obtain proper equalization during play- 
back. Transistors Ql and Q2 are 2N534, SK3003, 
GE-2 or HEP-254. 



back to the emitter of Ql and determines 
the gain of the circuit In this case 22 
kilohms was chosen to set the gain at 150, 
but other values of gain may be obtained 
by adjusting die value of this resistor. 

Equalized audio amplifier 

The equalized audio amplifier shown in 
Fig. 19 is a two stage direct coupled audio 
amplifier with a frequency selective feed- 
back path. It is particularly suitable for 
boosting and equalizing the signal from a 
ceramic phono pickup to obtain a flat output 
of sufficient level to drive an audio power 
amplifier. 

When playing a record, the output from 
the pickup is proportional to the force to 
which the stylus is subjected when tracing 
the groove. In fact, the open circuit voltage 
across the pickup is approximately propor- 
tional to the logarithm of the frequency 
with reference to the recorded amplitude. If 
the pickup is loaded with a very high im- 
pedance on the order of one or two megohms, 
the output versus input is nearly the in- 
verse of the recording characteristic; there- 
fore, the equalization is automatic* 

However, it is not always possible to load 
the pickup with a very high impedance cir- 
cuit, especially when transistors are used 



-6V O— f* 



Stl 




01 - 2N2429 

02 - 2N2706 

03 - 2NE430 



Fig. 20, This complimentary amplifier provides up 
to 220 mW output with a frequency response from 
90 Hz to 12.5 kHz, Although matched transistors 
are not required for Q2 and Q3, they are available 
as the 2N2707. 



8A 



73 TRANSISTOR CIRCUITS 



in the preamplifier. Resistive pads may be 
used to increase the input impedance, but 
they greatly reduce stage gain and increase 
problems with signal to noise ratios. 

In the amplifier of Fig* 19 equalization 
is obtained by a frequency selective feed- 
back path between the collector and base 
of Ql- Stabilization at dc is provided by 
the direct coupling between Ql and Q2 and 
the current feedback path through the 10 
ohm resistor in the base of Ql. In addi- 
tion, more negative feedback is provided 
by the unbypassed emitter resistor in the 
second stage. 

Complementary power amplifiers 

The small transformerless complementary 
amplifier illustrated in Fig, 20 provides an 
output of 220 raW with an input of only 
40 microamps. The transistors in the single 
ended class B output stage are used in the 
common collector configuration and are 
biased by a resistive voltage divider and 
the driver transistor circuit. The emitter 
resistors in the output stage provide ade- 
quate temperature stability and are estab- 
lished by cut and try, but a value of 2.7 
ohms seems to offer a good compromise. 
In adjusting this amplifier, the 100 ohm 
pot should be adjusted so that the idling 
current of the output transistor is on the 
order of 2.5 mA; this will insure a mini- 
mum of crossover distortion. When properly 
adjusted, this amplifier will exhibit a ±3 



-3 O- 




l«0B32 
OHMS 



m 



Ql - 2N£429 

02- 2NZ7Q6 

03- 2N2430 



Fig, 21. This 470 mW complementary audio am- 
plifier exhibits less than 2% distortion and is 
flat within 3 dB from 15 Hi to 130 kHz. 



1 

R. < Q2 T*"- 





N 



IJ5V 



*W-v 1- 

4.7k t 



8a 



.75V 



Fig, 22. An audio power amplifier with push pull 
output using a single transistor in the final stage 
may be obtained with this simple circuit. Only 
about 50 mW is available from this amplifier, but 
the gain is flat up to 30 kHz. Both Ql and Ql 
should be germanium audio transistors such as 
the 2N215, 2N404, 2N2953, SK3004 or HEP-253. 

dB frequency response from 90 Hz to 12.5 
kHz and distortion of 4% at 120 mW input 
and 10£ at 220 mW input 

Another complementary audio amplifier 
is shown in Fig, 21* This power stage pro- 
vides 470 mW output and utilizes both ac 
and dc feedback to minimize distortion and 
extend frequency response. Although un- 
matched transistors are not required for 
the proper operation of this amplifier, a set 
of matched transistors is available as the 
2N2707; the cost of the matched pair is 
only several cents more than the total sep- 
arate costs of a 2N2706 and 2N2430. This 
very useful amplifier is flat ±3 dB from 
15 Hz to 130 kHz, exhibits an input im- 
pedance of 750 ohms and produces less than 
2% distortion at 470 mW output 

Single transistor push pull 

The amplifiers illustrated in Figs* 22 and 
23 illustrate how a quasi-push-pull output 
may be taken from a single transistor. 



OS 



« — IHr 




Fig, 23. A larger power version of the single tran- 
sistor push pull circuit of Fig. 22 is shown here. 
The operating characteristics are similar to the 
50mW circuit except that approximately I watt 
may be obtained. Transistors Ql and Q2 are 
2N2I5, 2N404 P 2N2953, SK3004 or HEP-253; Q3 
is a 2N554, 2NI032, 2NI666, SK3009 or HEP-232. 



73 TRANSISTOR CIRCUITS 



9A 



^ 



VDF1 * GL 6BP50IO. OR EOUfV 




INPUT 



Fig. 24. This line operated 
audio power amplifier pro- 
vides about 500 mW out* 
put with an 80 millivolt 
input signal. Q I is a 
2N3565, SE4002, SK3020 or 
HEP-54; Q2 is a 2N39I6 
or SE7005. 



These amplifiers arc tic connected, thereby 
eliminating many components, while at the 
same time assuring excellent low frequency 
response. 

In the circuit in Fig. 22, the first transis- 
tor serves as both an ac driver and part 
of the dc bias system. Although the values 
shown in the schematic were selected for 
optimum results, the 6800 ohm biasing re- 
sistor (Rl ) should be adjusted experimental- 
ly to obtain equal voltages across the col- 
lector and emitter loads as illustrated in 
the schema lie. 

The frequency response of this amplifier 
may be adjusted by changing the value of 
the 0.05 ^F capacitor (CI), When this ca- 
pacitor is left completely out of the circuit, 
the heavy negative feedback around the 
circuit provides a frequency response that 
is flat from dc (with the input capacitor 
shorted) to 30 kHz, However, under these 
conditions, the gain is only about 35 dB. 
The maximum power output available from 
this circuit is on the order of 50 mW; above 
this level severe clipping occurs with notice- 
able audible distortion. 

A higher power circuit that exhibits es- 
sentially the same characteristics is illus- 
trated in Fig. 23. With properly heat sinked 
transistors, this unit provides usable out- 
puts up to one watt. As with the lower 
power circuit, the bias resistor (Rl) should 
be adjusted to provide equal voltages across 
the emitter and collector loads shown in the 
schematic. 

The input impedance of both these cir- 
cuits is on the order of several thousand 
ohms, so they may be easily driven by other 
transistor circuits. Although two separate 
speakers are shown us the output load, the 
load could just as easily be two separate 
transformer windings. 



Line operated amplifiers 

The line operated one watt amplifier in 
Fig. 24 provides about 500 m\V output with 
an 80 rnV input signal. The use of transis- 
tors with high collector to emitter voltage 
ratings permits the use of a transformerless 
power supply operating directly from the 
115 volt ac line. To prevent damage to Q2 
in the event of transient voltage spikes on 
the line, a voltage dependent resistor (VDR) 
such as a General Electric Thyrector or 
Motorola Thyristor should be connected 
across the primary of the output trans- 
former. 

Another line operated power amplifier 
is illustrated in Fig. 25. This amplifier is 



♦ IOO v 



J 1 




0I-2N2925, 2*3391, 2N3392 

ere- 2*29*4, 2N£Tt£, 2*3393 

03~2N£923, 2N2926 

04-2N4054 

Tl -2500 olimt TO VOICE COIL 

Fig, 25. High performance with low cost is ob- 
tained with this line operated audio power am- 
plifier because expensive electrolytic capacitors are 
eliminated by direct coupling between stages. This 
circuit delivers I watt to the speaker with 3 mW 
input. 



I0A 



73 TRANSISTOR CIRCUITS 






-it V 







m 



01,02,03 2HI09, 2N2CI3, 2N2953, SK30G4 

Tl £5* 1200 OHMS 

T2 EO K 2K OHMS CT 

T3 5K CT ZOO OHMS CT 

Fig. 26. This 100 mW modulator may be used to 
collector modulate transmitters up to about 200 
mW or to base modulate somewhat larger power 
amplifiers. Good performance with a minimum of 
components is obtained by transformer coupling 
between stages* 

based on the use of a high voltage plastic 
transistor, the 2N4054. The circuit delivers 
one watt of audio power to a speaker with 
about 3 millivolts input signal; at this power 
level the total harmonic distortion at I kHz 
is less than 105£. The key to its low cost 
performance is the fact that direct coupling 
is used, thereby eliminating the need for 
expensive electrolytic capacitors. 

Modulators 

The 100 milliwatt modulator illustrated 
in Fig. 26 is suitable for collector modulat- 
ing small transistor transmitters up to about 
200 milliwatts. It may also be used for 
base modulating somewhat larger transmit- 



ters. The circuit is relatively straight for- 
ward, with a single audio amplifier driving 
the class B push pull power stage through 
a small transformer. To modulate the col- 
lector of a small transmitter, simply run the 
collector voltage supply through the second- 
ary of the "moduation" transformer, in this 
case a low cost 5k: 200 ohm audio trans- 
former. 

The 5 watt modulator shown in Fig* 27 
may be used to modulate transmitters with 
up to 10 watts input. The use of low cost, 
high gain silicon transistors and efficient 
transformer coupling significantly decreases 
the complexity of the circuit. Usually many 
more transistors are required to obtain five 
watts of audio with a microphone input. 
Although this modulator was designed for 
a ceramic or crystal microphone, it may 
be used with dynamic types with slightly 
less gain. This circuit exhibits extremely 
low distortion characteristics, and when used 
to collector modulate a ten watt transistor 
transmitter, produces extremely clear and 
crisp audio. 

The transistorized 25 watt modulator 
shown in Fig. 28 is not much different 
from other types which have been described, 
but with three transformers it is somewhat 
more efficient than most. The transformers 
are readily available commercial models 
which may be obtained from most suppliers. 
However, transformer T2 must have a center 
tap on the secondary; this is easily accom- 
plished by unwinding 46 turns from the 
outside winding, bringing out a center tap 
at this point and rewinding. Impedance 
matching to the rf amplifier is accomplished 
by adjusting the rf output loading network. 



MIC© 




*oonCT:25ncT 

o 



m 



OS 



+ I2V 



II 

XMTft 8* 



Qi 2N3335, 2N3693, 5E»00< 

QZ 2N3404. SE600I 

03,04 2KZ8G8, 2H3UO, 2N3923 

Fig, 27. 5 watt modulator for transmitters up to 10 watts input. High gain silicon transistors and 
transformer coupling increase performance at decreased circuit complexity. 



73 TRANSISTOR CIRCUITS 



IIA 



OUTPUT 



THOHDARSOW 
TR-5 




Iil5Vl 



+ (Z.€ 



Fig, 28. 25 watt modulator uses readily available 
commercial transformers. Transistors Ql and Q2 
are 2NII72, 2N30I, 2NI560, SK3009, GE-9 or 
HEP-232r Q3 and Q4 are 2NI74, 2N278, SK30I2 ( 
GBA or HEP-233* 

The frequency response of this circuit is 
quite good and is essentially flat from 200 
Hz to 7 kHz. 



Circuits for Receivers 

Injection oscillator 

If you are interested in building a dual 
conversion receiver for single channel op- 
eration on MARS, 2 meter FM or WWV, 
the single oscillator circuit which provides 
two outputs illustrated in Fig, 29 should be 
of interest This single oscillator circuit re- 
sults in a reduction of components without 
sacrificing receiver performance. Basically 
it consists of a conventional common base 
transistor oscillator which provides the in- 
jection voltage for the second mixer. The 
output of the oscillator is fed into a diode 
harmonic generator and resonant tank which 
is tuned to the desired harmonic; this har- 
monic is used for injection into the first 
mixer. For example, for a dual conversion 
15 MHz WWV receiver with a 455 kHz 
if, a 3636 kHz cystal would be used along 
with its third harmonic at 10.908 MHz. The 
10.908 MHz signal would be mixed with 
the 15 MHz WWV signal in the first mixer 
to provide an output at 4092 MHz; this 
signal would in turn be mixed with the 
3636 kHz oscillator output in the second 



mixer to provide the 455 kHz if. The only 
consideration in choosing the crystal and 
harmonic frequencies is that only odd har- 
monics should be used. This is because when 
even harmonics are used in this scheme, 
poor second if image rejection will be a 
problem. 

In most receivers the oscillator injection 
frequencies are below that of the signal 
frequencies. This is usually desirable since 
it results in a lower &st if frequency which 
will provide better image rejection. In this 
case the necessary crystal frequency may 
be found from the following formula: 



f* = 



fa — lif 

h+ 1 



Where: f« = 

f. = 

f<r = 

h = 



Crystal frequency 

Signal frequency 

if frequency 

Harmonic to which diode 
tank circuit is tuned. 



In those cases where it might be desirable 
to have the injection frequencies higher than 
the signal frequencies, the following formula 
may be used: 



h = 



fi — ft; 

h-l 






BFO's 



The simple BFO in Fig, 30 may be added 
to an existing receiver with a minimum of 
cost and effort Essentially it is a tuned 
collector oscillator with an if transformer 
being used for the tuned circuit inductance. 
Just pick a transformer that is compatible 
with the if in your receiver; it doesn't make 
any difference to the transistor. Anything 
between 85 kHz and 1600 kHz will work 



22 k 




i 



3 



4.7* XTAL 




JDZ 



Fig. 29. Single oscillator and diode provide two 
Injection frequencies for dual conversion receivers. 
Transistor Q! is a 2NI745, 2N2I88, TIM 10, GE-9 
or HEP-2; the diode should be a IN82A or similar. 



I2A 



73 TRANSISTOR CIRCUITS 




Fig. 30, This beat frequency oscillator may be 
added to existing receivers with a minimum of dif- 
ficulty. The BFO frequency is determined by the 
if tramformer which provides feedback from col- 
lector to emitter. Transistor Ql should be a 2N384, 
2NI749, 2N2362, TIM 10, SK3008, GE-9 or HEP-2. 

well in this circuit* Before you can use 
the transformer though, remove all of the 
fixed tuning capacitors from the unit; usual- 
ly these are readily available on the bottom 
of the transformer, If the circuit does not 
oscillate when voltage is applied, reverse the 
transformer leads going to the emitter of 
the transistor. To connect the BFO into the 
receiver, run a piece of small coaxial cable 
from the BFO output to the base (or grid) 
of the detector. In some cases sufficient in- 
jection will be obtained by just placing the 
coax lead in the immediate vicinity of the 
detector. Adjust the core in the BFO trans- 
former so that the variable tuning capaci- 
tor allows the BFO output to swing to either 
side of the receiver if; then the variable 
capacitor will operate as a pitch control 



+ 2QV 




4.7K 



-OOUTPUT 



QI-£Nem, £N3392 



FREDUCNtr 


: 


C8 


L 


50 khi 


3500 pf 


1500 pf 


tO mH 


60 kHz 


£200 pt 


910 pf 


6.2 fnn 


100 kHi 


IflQO pf 


750 pf 


4.7 mH 


£00 hKr 


910 pf 


390 pf 


2-2 mH 


455 hHt 


390 pf 


160 pf 


t HlH 


1000 kHz 


IBO pf 


75 pf 


047 mJ* 



1 > i I 

Fig. -*3 1* This simple circuit provides an extremely 
stable BFO. The frequency of oscillation may be 
tailored to your needs by simply choosing the 
proper tank components listed in the table. 



+ fZO 



4.7 k 
SIGNAL INPUT O VW 



AGO 



LONG TIME CONSTANT 
I 1 





L__ __ WH 



Fig. 32. This super AGC circuit only requires two 
transistors to obtain up to 60 dB of control. 9 1 
and <?2 are 2NI6I3 or HEP-254. 

* The circuit illustrated in Fig. 31 repre- 
sents a temperature stable Colpitis oscilla- 
tor which is very useful as a BFO. This 
oscillator utilizes an inexpensive silicon plan- 
ar transistor and is exceptionally stable over 
wide ranges in temperature. In addition, 
it is characterized by a large output ampli- 
tude (10 volts peak to peak) and low 
harmonic distortion. In addition to duties as 
a beat frequency oscillator, this circuit is 
useful where a stable signal source is re- 
quired up to several MHz. The 20k emitter 
pot is an output level control; the 10k pot 
in the base bias leg is used to adjust the 
base bias for maximum amplitude output. 

AGC circuit 

The super AGC circuit shown in Fig, 32 
requires only two transistors to obtain 60 
dB of control, while maintaining low dis- 
tortion and power requirements. When a 
signal appears at the input with its corre- 
sponding AGC signal on the input of the 
long time constant circuit, Ql conducts and 
causes current to flow through the diode. 
This current flow lowers the impedance of 
the diode and provides a low impedance 
path between the amplified signal at the 
collector of Q2 and the input signal at its 
base. When the diode conducts heavily, 
there is nearly 100% feedback and the 
gain of this stage is nearly unity. In addi- 
tion, the input impedance of the stage be- 
comes very low and results in a large volt- 
age drop across the series connected 4700- 
ohm resistor. 

When the collector current of Ql is re- 
duced to zero, the feedback through the 
diode is negligible and the gain and input 
impedance of Q2 is the same as that of 
a standard common emitter amplifier. With 



73 TRANSISTOR CIRCUITS 



I3A 



-ao — 



LAST IF 



OflrvEft 
XFMR 




AVCO- 



SOUCLCM ADJ 




66h 



Fig, 33, This simple squelch circuit may be added to any transistorized receiver with only minor 
changes; in most receivers only four additional components are required, two resistors, a capacitor 
and a transistor, Ql is an existing transistor in the receiver; Q2 is a 2N404, 2N2953, SK3004, SE-2 
or HEP-254, 



the constants shown in the schematic, a 60 
dB control range is provided by a to 100 
mA AGC input. To increase this range, high 
gain transistors and a higher voltage power 
supply must be used. 

Squelch circuits 

The simple, but positively acting squelch 
circuit in Fig* 33 may be added to any 
transistorized receiver with only minor 
changes in the audio section and four addi- 
tional components. Without an input signal, 
normal forward bias to the */ amplifier flows 
in the AGC line. A portion of this bias 
voltage is applied to the base of Q2 through 
the 10K ohm squelch adjust* This voltage 
biases Q2 into full conduction with the 



squelch control pot determining the degree. 
When Q2 is saturated, base bias for Ql 
is diverted to ground so the driver cannot 
amplify incoming noise and the speaker is 
quiet. When a carrier large enough to cut 
off Q2 is received, Ql conducts and ampli- 
fies normally. The 100 ^F filter capacitor 
in the base of Q2 removes all but the AGC 
signal coming from the detector. 

To make the squelch less sensitive to 
large noise pulses, resistor Rl will ensure 
that transistor Ql will be cut off until rf 
operates the squelch. The value of this re- 
sistor should be determined experimentally, 
since its value depends upon the type of 
transistor used in this stage. 

Another simple squelch circuit is illus- 
trated in Fig, 34. When there is no signal 



lHf^> 




+ _T0 AUDIO 
AMP 



O-ll 



Fig. 34. This squelch circuit is very versatile and is capable of squelching out a 300 ^V signal 
and still maintain control down to less than I j*¥. With the 2,5K pot set to squelch out a signal, 
approximately 3 dB increase in received signal will override the squelch. Q2 is a 2NI304, SE-5 
or SK30II; <?3 is a 2NI274; GE-2 or HEP-254. 



I4A 



73 TRANSISTOR CIRCUITS 



-90 




O OUTPUT 



Fig, 35, This audio filter uses a 1 000 Hi 

bridge circuit to provide bandwidth; from 



600 Hz wide. Ql and Q2 
SK3004, GE-2 or HEP-254. 



Wien 
70 to 
are 2N406. 2N26I3, 



coming into the receiver, the AGC con- 
trolled if amplifier Ql is operating at maxi- 
mum gain. Under this condition the voltage 
drop across Rl is also maximum and is 
used to turn Q2 on. The current through 
Q2 is determined by the squelch control, 
R2, If R2 is set so that the current flow 
through Q3 causes the voltage drop across 
the 3,9k emitter resistor to be greater than 
the base voltage of Q3, it will be turned 
off. Under these conditions, there will be 
no output from Q3 and the receiver will 
be quiet* 

When a signal is picked up by the re- 
ceiver and the AGC is operating, the cur- 
rent through Ql is reduced according to 
the signal strength of the received signal 
This in turn reduces the voltage across Rl, 
reduces the current through Q2 and lowers 
the voltage on the emitter of Q3. When the 
emitter to base junction of Q3 is forward 



biased, the stage turns on and results in an 
output to the audio ampUfier. 

This circuit is very versatile and is capable 
of squelching out a 300 mV signal into the 
receiver and still maintain control down to 
less than 1 /*V, In some cases there may 
be some audio distortion between the on 
and off conditions of Q3, depending upon 
the setting of the audio gain control. This 
distortion is not ordinarily objectionable 
however and when the signal is several times 
greater than that required to just trigger 
the squelch, it is not present 



Selective audio amplifier 

Selective transistor amplifiers are very 
helpful in sorting out stations from the 
QRM that plagues our HF bands. They are 
also quite helpful in VHF and UHF work 
for effectively narrowing the bandwidth of 
the receiver. This is because as the band- 
width is narrowed, the noise in the receiv- 
ing bandpass is reduced accordingly. 

In the selective transistor amplifier illus- 
trated in Fig. 35, the frequency selected is 
determined by a modified Wien bridge cir- 
cuit in the collector of the first transistor. 
Although the constants shown in this cir- 
cuit are for a center frequency of 1000 
Hz, other frequencies may be selected by 
the proper choice of bridge components. 
The bandwidth of this circuit is determined 



M,X£R 





MECHANICAL 

FILTER 
ADAPTOR 



FJRST l,ft 




'FIRST 455 *Mt 
* UF. XFMR 



A mH. TAPPED 40% UP 
FROM COLD END 
(SEE TEXT) 



-0+9 



£ 20 



h 40 



u 
£ 60 



BO 



(CENTER FREQUENCY- 4 SSkHi] 














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10064 20246 
FREQUENCY U till 



8 K> 



Fig f 36* The selectivity of Inexpensive communications receivers may be substantially increased 
by the addition of this mechanical filter adapter. The transistor is used to make up for the 10 dB 
toss through the titter. The typical passband of a receiver without the filter is shown by A in 
the frequency response curvej the mechanical filter adapter results in curve B* Ql should be a 
2NI638. 2NI727. SK3Q08 or HEP-3. 






73 TRANSISTOR CIRCUITS 



ISA 



I.F. AMPLIFIER 





+ 12 



OOUT 



m 100k 

REMOTE PHASE ADJ. 



(A) 

Fig. 37. Usually the crystal filter circuit in a receiver (A) must be physically located so the 
phasing capacitor (C P j is accessible to the front panel. By using the varactor phased filter in B, 
the crystal may ba located in any convenient location. Ql and Q2 are 2N3478, 2N35M, 2N3707, 
40236 or HEP-50; Dl Is a 20 pF varactor such as the IN954 or TRW V20. 



by the value of the input load resistor, but 
with the resistors shown ? it may be varied 
between 70 and 600 Hz, 

Mechanical filter adapter 

With the heavy QRM that is rampant 
on today's high frequency ham bands, the 
selectivity of many of the lower cost com- 
munications receivers leaves a great deal 
to be desired. In fact, in many cases the 
selectivity of these receivers is hopelessly 
inadequate. Adding a Q multiplier or a 
simple crystal filter will help to some ex- 
tent, but these devices simply narrow the 
peak of the if response curve. Although this 
is quite suitable for CW work, it is of 
little help in separating SSB and AM sta- 
tions. A much more useful improvement is 
the addition of a mechanical filter to the 
receiver if. Unlike simple LC circuits, the 
mechanical filter closely approximates the 
ideal bandpass response curve. 

Wiring this filter into a receiver could 
require some pretty extensive rework, but 
by using the transistorized mechanical fil- 
ter adapter illustated in Fig, 36, it may 
be simply plugged into the first if amplifier 
tube socket The actual circuit itself is very 
straightforward; the simple transistor am- 
plifier makes up for the 10 dB of loss through 
the mechanical filter. Coupling the output 
of die transistor to the grid of the first 
if tube is accomplished with the 4 mH coil. 
This may be made by winding 100 turns 
of number 36 on a cup core r toroid 
{tapped at 40 turns) or the primary of an 
inexpensive 455 kHz if transformer may 
be used. 

Layout of the circuit is not at all critical 
except that care should be taken to make 



sure that there is no leakage around the 
mechanical filter and amplifier. To this end 
the plate lead of the if tube should be 
shielded. Although the base layout shown 
in the schematic is for a 6BA6 tube, this 
adapter may be used with any # tube by 
simply placing the mechanical filter in the 
grid lead. Packaging this device is quite 
simple too; just mount an appropriate tube 
socket on top of a plug-in can (Vector G2.1- 
8-4), build the circuitry inside, plug it in 
the receiver tube socket and pick the weak 
signals out of the QRM. 

Tunable crystal filter 

One of the problems encountered when 
installing a crystal filter in a receiver for 
added selectivity is the fact that the unit 
must be installed physically close to the 
front panel so that the phasing control (C») 
is accessible- This problem is neatly solved 
by using the varactor tuned unit shown in 
Fig* 37, In this circuit, the crystal is phased 
by the varactor diode which may be re- 
motely controlled by the variable resistor 
RL The circuit may be used for any if 
from 100 kHz to 1500 kHz by simply se- 
lecting a crystal which is resonant at the 
desired frequency. In addition, the filter 
may be completely removed from the system 
by simply forward biasing the diode. 

Cascode amplifiers 

One of the big advantages of the cascode 
rf amplifier is that in the high frequency 
range it does not require neutralization. 
In the cascode circuit shown in Fig* 38, 
two transistors are connected so that the 
mismatch between them reduces internal 






I6A 



73 TRANSISTOR CIRCUITS 



43 O 




Fig. 38. This cascode amplifier is extremely use- 
ful because it provides high gain without the need 
for neutralization. Q\ Is a 2N9I8, 2 N 3464, 2 N 34 78, 
MPS9I8. 40235 or HEP-56; Q2 is a 2NI742, 
2N2398, 2N2894 t 2N3399, TIMtO or HEP-2. 

feedback; therefore the input and output 
impedance of the circuit is essentially in- 
dependent of the source and load. 

In single transistor amplifiers the collec- 
tor to base capacitance causes internal nega- 
tive feedback that reduces amplifier gain 
at high frequencies. This feedback also 
causes the input and output impedances of 
the transistor to be dependent upon the 
value of the source and load impedances. 
Normally this negative feedback is neutral- 
ized out with a small amount of positive 
feedback external to the transistor. Unfor- 
tunately however, this process is long and 
tedious and often requires many adjustments. 

The isolation between several similar 
stages is particularly important where more 
than one stage is used, because as a multi- 



iNPUTO- 




■O -20 V 



4.5 jjH 
MILLER 4504 



0.0! 
-| ( O OUTPUT 



365 pf 



/77 



1.5 jiH 
MILLER 4502 



365 pf 



Fig. 39- This 30 MHi if stage uses two FETi con- 
nected in the cascode arrangement to provide 
20 dB gain without neutralization; the bandwidth 
is 4 MHz. Both FEFs in this circuit are 2N38I9, 
MPFI05 or TI534. With a negative supply voltage, 
the 2N4360 or TIM 12 would be suitable. 



WPUTO 




-O-30V 



T-1-l2.5jiH 
MILLER 4309 



"*****'* 



39K 



A 



o.i 

-|( OQvTpyr 



r 



Fig. 40, This cascode video amplifier provides 
more than 6 MHz bandwidth with a voltage gain 
of ro. Both FEFs are 2N38I9, MPFI05, TIS34 or 
HEP-80I, A negative supply would permit the use 
of a 2N4360 or TIM 12. 

stage amplifier is being aligned, the tun- 
ing of one stage effects all the other stages. 
With the cascode rf amplifier, this short- 
coming is overcome. Moreover, the gain of 
the cascode circuit is greater than the gain 
of a neutralized common-emitter stage with 
the same stability- 

Since the emitter of Ql is tied directly 
to the negative supply, the base can be 
connected directly to the output of the previ- 
ous stage which is at ground potential. 
This eliminates a coupling capacitor and 
speeds up circuit recovery time after an 
overload. In addition, the gain of the stage 
may be controlled by varying the amount 
of current through Ql (by adjusting the 
value of the negative supply). 

The high gain cascode circuit shown in 
Fig, 38 uses two very inexpensive transistors 
to obtain 15 dB gain at 100 MHz with no 
neutralization; at lower frequencies the 
gain will be somewhat higher. No values 
are shown for the tuned circuits because 
they will be different for each application, 
However, dc biasing is usually the toughest 
part of any amateur transistor circuit de- 
sign, and that is already done; all you 
have to do is put some tuned circuits in. 
The tap point on the input inductor, should 
be chosen for best noise figure, The tap 
on the output inductor is chosen for maxi- 
mum power gain. 

Another somewhat different cascode cir- 
cuit is illustrated in Fig. 39. This cascode 
30 MHz if amplifier uses FETV and is 



73 TRANSISTOR CIRCUITS 



I7A 



no 



MO. * 
V* CHA 




Fig. 4L This simple one transistor superregenera- 
five receiver for two meters may be used for copy* 
ing many local signals. With the components 
shown, this receiver will tune from about 90 to 
150 MHi. It may be used on other frequencies 
by changing the inductor and capacitor as de- 
scribed in the text, Ql is a 2NI742, 2N2398, 
2N3399, TIM 10, &E-9 or HEP-2. 

characterized by a 20 till power gain, band- 
width greater than 4 MHz, and all without 
the necessits for neutralization. For even 

r 

more gain, these stages may be simply 
cascaded, 

The cascode video amplifier shown in 
Fig, 40 is almost an exact replica of the 
vacuum tube circuit that was originally de- 
veloped in the 1940's. Usually a single triode 
is avoided m wideband or video amplifiers 
because the input capacitance and its multi- 
plication by device gain (called Miller ef- 
fect) seriously loads the input; With the 
cascode configuration, the input capacitance 
is no longer multiplied by the gain of the 
device, but is limited to the input capaci- 
tance of the FET\ With the shunt peaking 



3*» 



2-l/Z" 0IA, 
4-3/4" HIGH 




5 TURNS NO. 16 4W3 ON 1/4" 
SLUG -TUNED FORM WITH 
I TURN LOOP ON COLD END 



l/B TO 3/* B CHA. 




10* 
GAIN 



Fig* 42. Low neise two meter preamplifier uses a 
beer can cavity to provide excellent dlscriminatoin 
against nearby kilowatts, Ql it t 2N3478, 2N356? 
2N3564, 40235 or SK30I* 



inductance shown (Miller 4309), this circuit 
is characterized by a voltage gain of 10 
with a 3 dB bandwidth of over 6 MHz. 
The value of the inductance shown should 
work with most loads, but in some cases 
the bandwidth may be increased by chang- 
ing its value slightly. 

Two meter superregenerative receiver 

The simple little receiver shown in Fig. 41 
was designed primarily for the two meter 
band, but with appropriate changes in the 
input rf coils, it will work equally well 
on any frequency between 28 and 160 MHz. 
Basically, Ql is a common base oscillating 
detector stage which quenches at about 25 
kHz. The audio output from the detector 
is coupled across the transformer to the 
simple two stage audio amplifier. For more 
audio output, a 500 to 3,2 ohm transformer 
may be connected between Q3 and the speak- 
er. The 20 kilobm pot should be adjusted 
for a total current drain of about 30 mA. 
With the circuit constants shown in the 
diagram, this receiver will tune from about 
90 to 150 MHz. To cover six meters, the 

should be changed to a 
the number of turns on 
6?i. Since this is a re- 
generative receiver, it must be completely 
enclosed in a metal box to avoid the un- 
desirable effects of hand capacity. 

Two meter preamp 

The two meter preamplifier of Fig, 42 
uses inexpensive transistors in the common 
base configuration, yet provides noise figures 
that are nearly optimum for this band. The 
coaxial input cavity is easy to build and will 
provide more than adequate selectivity 
against your high powered neighbors on two. 
Although this input cavity may be built 
from scratch, the easiest approach is to use 
a spent beer can. Be careful when choosing 
the can though, some brewers are using 
aluminum cans wich are pretty difficult 
to solder. The whole amplifier may be 
mounted on a small piece of epoxy board 
and then the entire assembly attached to 
the outside of the cavity, 

220 MHz rf amplifier 

The 220 MHz rf amplifier shown in Fig. 
43 exhibits about 17 dB gain, although the 
exact amount will depend upon the type of 
transistor used. Optimum operation lot low- 



tuning capacitor 
15 pF unit and 
L2 increased to 



ISA 



73 TRANSISTOR CIRCUITS 



L2 




001 

-T- 



,001 



I 



* 




LI 3-1/2 TURNS NO 16, 1/4 B D*AM, 1/2* lOK» 

TAPf^ED AT CENTER 
L2 i'l/4 TURNS NO £4 OM 1/4" SLUG-TUNED FOftW. 

L3 9 TURNS NO. >€, t/S" WAAL 7/t* LONG TAPPED 
ONE TURN FROM CXXO END. 

01 2NM7B, 2N3564, 40253 
RFC 84 jiM (OHMITE 2*220} 

Fig* 43. Low noise 220 MHz preamplifier. This 

circuit will provide extremely high gain with low 
noise on the M/| meter band, Neutralization is 
controlled by inductor L2. 

est noise figure also depends upon the 
transistor type, but usually will be in the 
vicinity of 6 volts collector voltage and 1 
inA collector current. Unfortunately, this 
is usually not the same operating condition 
for maximum gain; maximum gain will oc- 
cur at somewhat larger values of collector 
voltage and current. When this amplifier is 
set up, the 470k base bias resistor should 
be adjusted for the condition that you are 
looking for, whether it be minimum noise 
figure, maximum gain or a compromise be- 
tween the two. Remember that for most 
practical receivers the noise figure will he 
dictated by the noise figure of the first 
rf stage; more gain can be added by another 
stage of amplification. 




o-*v 



OUT 



Fig. 44. This untuned crystal oscillator will oscillate 
with any crystal from 300 kHz to 10 MHz. Fre- 
quency stability is very good because the emitter 
follower buffer amplifier effectively isolates the 
oscillator from the load. Ql and Q2 are 2N993, 
2NI749, 2N2084, 2N2362, TIM 10, GE-9, SK3006 
or HEP-2. 

connected as an emitter follower. With this 
arrangement, Q2 acts as a buffer stage 
and quite effectively isolates the oscillator 
from the load. 

Another untuned crystal oscillator stage 
is shown in Fig. 45. This circuit will oscil- 
late with any crystal between 3 and 20 
MHz with no tuning whatsoever. If over- 
tone crystals are plugged into the circuit, 
they will oscillate on their fundamental fre- 
quency. For overtone crystals up to about 
60 MHz, the fundamental will be approxi- 
mately Ji the marked frequency; above 60 
MHz the fundamental is normally about Js 
the marked frequency. For best stability with 
each of these untuned crystal oscillators, 
all the capacitors should be high grade silver 
mica types. 

The crystal oscillator shown in Fig. 46 
has proven to be extremely stable and easy 
to adjust Basically it is a standard Colpitis 
circuit with the frequency determined by 
the crystal. By using the appropriate induc- 
tors and capacitors, this circuit will oscillate 



Circuits for Transmitters 

Crystal oscillators 

A compact untuned crystal oscillator is 
a verv useful unit to have around the shack. 

m 

The oscillator illustrated in Fig. 44 does 
not have any tuned circuits, so almost any 
crystal from' 300 kHz up to 10 MHz will 
oscillate satisfactorily. It can be used for 
driving transmitters, as a signal source or 
for just testing crystals. In this circuit the 
first transistor is operating as an untuned 
crystal oscillator with the second transistor 




XTAL 



O OUTPUT 



RFC 
2.5 mH 



Fig, 45. This crystal oscillator will oscillate with any 
crystal between 3 and 20 MHi with no tuning what- 
soever; overtone crystals will oscillate on their 
fundamental in this circuit, Ql is a 2NII77, 
2NII80, 2NI742, GE-9, SK3006 or HEP-2. 



73 TRANSISTOR CIRCUITS 



I9A 



01 - 2N70B f 2N3364, £N38S4 ( 40E5T 

T 



IOK^.001 




FREQUENCY 


CI 


C2 


C3 


LI 


MILLER 
NO. 


L2 


10 -13,5 MHi 


30 pf 


300 pf 


01 


5,0- 9,0 jiH 


4505 


4H/2T 


135- IB MHz 


30 Of 


300 pf 


0! 


2 9-50pH 


4504 


3T 


Ifl - 24 MHz 


30 pf 


300 pf 


.01 


1.6-2j8jiH 


4503 


2-i/2T 


£3.5- 32 MHz 


lOpf 


100 pf 


.01 


2.8- 5,0 pH 


4504 


3T 


32 - 42 MHi 


lOpf 


100 pf 


,001 


I 6-28|iH 


4503 


2-I/2T 


42 - 53 MHi 


1 pf 


100 pf '001 


1.0- t.6jjH 


4502 


2T 


56 - B4 MHz 


io pr 


too pf .001 
1 


0.4-aSpH 


4501 


1 -I/4T 



Fig. 46. This Colpitis type crystal oscillator may 
bo used with either fundamental or overtone crys- 
tals from 10 MHi to 84 MHz with the tuned cir- 
cuit components listed. It oscillates quite readily 
when adjusted and provides a stable output. 



+ 20 



XTAL 




Fig. 47. This is the old familiar vacuum tube Pierce 
oscillator circuit with a field effect transistor in 
place of the thermionic trlode. Circuit constants 
shown here are for the I MHz region, but the tuned 
circuit may be adjusted to any frequency desired. 
Q I is a 2N4360 or TIM 1 2. 




-!2 



ANY SEfilES MODE 
OPERATING XTAL IN 
3RD t 5TH,7TH,9TH, OH 
NTH OVERTONE 



LI 
C1 



TUNED TO RESONATE WITH C2 - COLLECTOR TAP 
1/3 UP FROM COLD END 

CAPACIT1VE REACTANCE OF APPRO*. 90_n_ 
AT OPERATING ERECUENCV 



FRTO (ZAHl) 


50 


144 


220 


432 


a tpn 


36 


12 


8.2 


3.3 



Fig. 48- This crystal oscillator was designed spe- 
cifically for overtone crystals and will oscillate up 
to the llth overtone in the VHF range* Suitable 
values for CI are shown for the VHF bands; for 
other frequencies, CI should exhibit approximately 
90 ohms capacitive reactance for best results. 
Q I Is a TIM tO. TI400 or HEP-3. 



with either fundamental or overtone crystals. 
Although circuit values are only provided 
here up through 84 MHz, this circuit will 
operate well above 100 MHz with smaller 
values of capacitance; the only requirement 
is that they retain a 10 to 1 ratio in capaci- 
tance, For operation with a negative supply 
voltage, ground the 10 volt line shown in 
the schematic, lift the 1.2k and 47 ohm 
resistors from ground and tie them to the 
negative supply, PNP germanium transistors 
may also be used by reversing the supply 
voltage and changing the 10K base bias re- 
sistor to 33k. 

The untuned crystal oscillator in Fig, 47 
uses an FET in the familiar Pierce vacuum 
tube circuit. In this oscillator the drain to 
source capacitance and gate to source capaci- 
tance make up the feedback path with the 
amount of oscillator excitation determined 
by their ratio. This circuit cannot be used 
with conventional junction transistors be- 
cause their low input impedance severely 
loads down the crystal. 

The crystal oscillator shown in Fig* 48 
is designed specifically for overtone crystals 
and will work up through the eleventh over- 
tone. The circuit is completely n^ncritical 
except for the value of Gl which should 
exhibit approximately 90 ohms capacitive 
reactance at the operating frequency. The 
tuned circuit is tuned to the frequency of 
interest. The 5 pF capacitor from collector 
to emitter should be adjusted for maximum 
rf output; above about 200 MHz it may 
not be required. The constants shown in 
the schematic should cause oscillation with 
any overtone crystal in the VHF range, 
but in some cases a sluggish crystal may 
require adjustment of the 24k base bias 
resistor to take off every time power is 
applied. 

Variable crystal oscillator 

The variable crystal oscillator shown in 
Fig. 49 is a very useful circuit to the ham 
who wants a highly stable signal on two 
meters or 432. Although it will only tune 
about 50 kHz on two and 150 kHz on 432, 
it is adequate for many types of operation. 
On 432 for example, most operation is with- 
in a few kHz of 432.00 MHz. The circuit's 
operation is quite straight forward; the dual 
365 pF capacitor pads down the resonant 
circuit and pulls the crystal down in fre- 
quency. Just how much it is pulled down 
is determined by the inductor LI. For an 



20A 



73 TRANSISTOR CIRCUITS 




/_Q01 



Ql f 0Z-2N70e, 2NZ2I9, 
21^3662, 40237 



+ 12 V 



Fig. 49, This variable crystal oscillator (VXO) may 
be used to vary the frequency of an 8 MHz crystal 
4 or 5 kHz when the 365 pF dual variable is 
tuned through its range. When multiplied to two 
meters or 432, this provides a very stable variable 
frequency. For 8 MHz crysals, LI is a 20-25 uH 
slug tuned coil; L2 is chosen to resonate at 8 
MHz with the 30 pF capacitor. 



Table 1 



Crystal 



L L 



3.5 MHz 35-60 /tH Miller 4509 



5*0 MHz 24-35 jiH Miller 450$ 



8.0 MHz 16-24 fiH Miller 450? 



9.0 MHz 16-24 fiH Miller 4507 



*Wound on Va" slug tuned form. 



80 turns #36, 

tapped at 27 

turns 

62 turns #36, 

tapped at 21 

turns 

40 turns #36, 

tapped at 13 

turns 

36 turns #36, 

tapped at 12 

turns 



8 MHz crystal, this inductor should have 
a center value of about 22 ^H; it should 
exhibit relatively high Q at 8 MHz and 
be self resonant well above the crystal fre- 
quency- As this inductor is increased be- 
yond a certain amount, the crystal will lose 
control and the circuit becomes a rather in- 
ferior VFO, For best results LI should be 
adjusted so that the crystal is pulled 4 or 
5 kHz when the variable capacitor is tuned 
through its full range. 

The buffer amplifier is coupled to the 
oscillator through a 50 pF capacitor. For 
maximum frequency stability, this capaci- 
tor should be the minimum value that will 
provide adequate drive for your transmitter. 
With the 50 pF capacitor shown, approxi- 
mately 10 volts of 8 MHz drive should be 
available with the buffer tank tuned to 
resonance. Inductor L2 is chosen to resonate 
at 8 MHz with the 30 pF capacitor; the 
tap is % up from the ground end. 



Two frequency crystal oscillator 

In the two frequency crystal oscillator 
illustrated in Fig. 50, the bilateral char- 
acteristics of the transistor effectively pro- 
vide two separate common emitter stages. 
Either of the two frequencies may be se- 
lected by simply applying a positive or 
negative voltage to the circuit. 

When a positive voltage is applied, cur- 
rent flows through Dl to the emitter of 
the transistor. The tuned circuit consisting 
of L2, C2 and the crystal Y2 determine 
the oscillation frequency available at the 
output The other tuned circuit consisting 
of LI and CI is shorted out by Dl. In 
addition, since crystal Yl is connected be- 
tween the base and emitter, there is no gain 
to promote oscillation at its frequency. 

If a negative voltage is applied to the 
supply terminal, the transistor "inverts" it- 
self with the collector becoming the emitter 
and the emitter the collector. In this case 
LI, CI and Yl determine the frequency 
of oscillation* Diode D2 shorts out the other 
tuned circuit and the crystal Y2 is con- 
nected between the base and emitter of 
the inverted transistor; therefore, there is 
no output at Y2's frequency. 

Transistors may not normally be usea in 
the inverted mode because rather large 



±10 V 




MK 



/77 



f77 



01- 2N384 P 2N525, SK3G04 r Tl XMD3 
01,02- GENERAL PURPOSE SJLICQN DIQDES 

Fig. 50. This two frequency crystal oscillator 
changes frequency by simply reversing the supply 
voltage. When the supply voltage is changed, the 
transistor inverts Itself; usually transistors may not 
be used in the inverted mode, but in an oscillator 
a gain of only I or 2 is needed and this circuit pro- 
vides a novel and simple way of obtaining two 
frequencies from a single stage with a minimum 
of switching. 



73 TRANSISTOR CIRCUITS 



21A 



■i 



amounts of gain arc* desired. However, as 
an oscillator, the gain need only be sufficient 
to produce oscillation; this usually requires 
a forward current gain of only one or two. 
For this reason almost any germanium tran- 
sistor may be used in this application. Sili- 
con NPN transistors will also work, but op- 
eration will be just opposite to that de- 
scribed above. 

Diodes Dl and D2 limit the output voltage 
to about 0.7 volts, so for some applications, 
further amplification may be necessary. The 
tuned circuit values shown in the schematic 
are for a resonant frequency of 455 kHz, 
where this circuit provides an excellent 
method for upper and lower sideband selec- 
tion. It may be used on other frequencies 
by simply changing the values of inductance 1 
and capacitance in the tuned circuits. 

UHF oscillator 

The simple UHF oscillator circuit shown 
in Fig, 51 will deliver up to about 2 mW 
ol power at 1000 MHz. Although this amount 
of power is insufficient for some applica- 
tions, 2 mW is more than enough for many 
mixer and converter circuits. Manx transis- 
tor types, when selected, will oscillate up 
to 1500 MHz in this simple circuit. 

Ten meter transmitter 

The three watt ten meter transmitter shown 



+ 20 




RFC 



TUNED LINE 



rht 



Fig. 51. This simple UHF oscillator will provide 
about 2 mW up to 1000 MHz; some selected 
transistors will provide usable power up to 1500 
MHz or so. Q\ is a 2N9I8. 2N3478, 2N3564 or 
HEP-56. 



in Fig- 52 gets over the high rf power/high 
price hurdle by using three inexpensive 
transistors in parallel in the final stag 
The three paralleled transistors ased will 
produce three watts output with a 15 to 
18 volt supply and about 2.25 watts with 
a 12 volt supply. The rf drive is provided 
by a 28 MHz crystal oscillator and driver 
amplifier. For maximum efficiency, modu- 
lation is applied to both the final amplifier 
and driver through the modulation trans- 
former; about 1.5 watts of audio power is 
required for 100% modulation. Since the 
transistors used in this transmitter have 
an fr of 500 MHz, a similar transmitter 
could he built for six meters; the only 
change would be in the resonant circuits. 



u 

L2 

L3 

L4 

01 

Q£ 

05,04,05 



13 TURNS NO £• ON \/A m SLUG TUNEO FORM TAPPED AT 6-1/2 TURNS 

10 TURNS NO 26 ON 1/4* SLUG TUNED FORM TAPPED AT 5 TURNS 

9 TURNS NO. 24 ON 3/a" SLUG TUNED FORM. 

SAME AS L3. 

2N70B I 2N30G9, 2N354G, 2N3AS6 

2N364I, 2N22I? 

2N3£42,2«22ia 




MODULATION 
TRANSFORMER 



-0-KI4V 



Fig, 52. This throe watt ten meter Transmitter maintains 
three inexpensive silicon transistors in the final stage. 



high efficiency and low cost by paralleling 



22A 



73 TRANSISTOR CIRCUITS 



PRI-UT NO, 32 WOUND 

ON \/Z TOROID 

SEC- £4T NO. 32 WOUNO 

BIFILAR TO PBU 

2N3295 
90MH1 
3wW PfP 

T, ,^ 



Pfff-MT Nq. 52 WW/NO 

ON 1/2 TOftCMD 

SEC-I2T NO. 32 WOUND 

BIFlLAft TO Pfll. 



WH-20T MO. 22 WOWO 

ON 1/2" TOH01D 

SECIOT MO. 22 WOUNO 

BlFlLAft TO PRI. 



O.J3pH 



30MH( 
tOW PEP 



+260 




Fig. 53. This tan meter linear amplifier for SSB service uses transistors which were designed 
specifically for single sideband linear operation. Many junction transistors cannot be used satis- 
factorily for this application, because linear amplification at low power levels is a serious problem* 



Ten meter linear amplifier 

Up until the present time transistors 
haven't been used too much in SSB trans- 
mitters because linear amplification at even 
low signal levels has been a serious prob- 
lem. However, the transistors in the ten 
meter SSB power amplifier illustrated in 
Fig. 53 were designed specifically for linear 
amplifier service and perform quite well 
The measured distortion of these devices 
is less than three percent without feedback, 
which is somewhat better than tubes under 
the same conditions. 

Actually the circuit of this amplifier is 
quite straight forward. The only critical 
parts are the coupling transformers between 
succeeding stages, These are wound on small 
S" toroids which are suitable for use at 
30 MHz (Ami-tron T-50-2), Coupling be- 
tween stages must be very tight and the 



3-1/4 TURNS NO, IB 
TINNED, 1/2 DIA J/2" LS 
TAPPED 3M TURN 
FROM COLO CNO 



4 TURNS !/B" COPPER 
TUBING, 3/* DlA.I-l/4 U3 t( 
TAPPED H/4 TURN 
FROM COLO END 




+ 25 



lin 



ear 



Fig. 54. This ton meter single sideband 
power amplifier will provide up to 8 watts PEP. 
The power gain of the 2N2947 if 13 dB at this 
frequency, and the odd order distortion products 
are at least 30 dB below the desired output* 



transformers should be bifilar wound. Both 
the input and output of this unit are de- 
signed for 50 ohm coaxial line, so it fits 
in nicely with other equipment being used 
on ten meters. 

The ten meter single sideband linear 
power amplifier shown in Fig* 54 is capable 
of delivering an output power of 8 watts 
PEP. The power gain at this frequency is 
13 dB, and all odd-order distortion products 
are at least 30 dB below the desired out- 
put. 

The main difference between this ampli- 
fier and one designed for class C operation 
in CW, AM or FM transmitters lies primarily 
in the do bias circuit. For class C operation, 
the only dc bias normally applied is the 
collector supply voltage. The 18 mH rf choke 
and resistive divider in the base circuit 
would be omitted. The transistor is biased 
on by the driving signal on the base. This 
results in one of the big advantages of the 
transistor transmitter— if the driving signal 
is suddenly removed, the power amplifier 
merely shuts off and sustains no damage. 

To obtain linear operation, a small amount 
of forward bias is applied to the transistor. 
This is a function of the resistive divider 
and the isolating choke in the base circuit 
The bias is adjusted so that a small collec- 
tor current flows without any input driving 
signal; when a driving signal is applied, 
the transistor is biased on to full operating 
collector current In this circuit the 2N2947 
draws 20 mA with no drive and 350 mA 
with full drive. 



73 TRANSISTOR CIRCUITS 



23A 




Hi 



+ £8 



9-1/2 TURNS NO. * 
CLOSEWOUNO ON 
1/4' FORM 



SOA 




Fig* 55. This 6 meter transmitter provides up to 50 watts of power with very good efficiency 
and very low harmonics. The 2N3950 in the final provides a minimum power gain of 8 dB on six 
and is rated at 50 watts continuous service. 



Six meter transmitter 

The six meter transmitter of Fig. 55 will 
provide 50 watts of power into the antenna 
with very good efficiency and very low har- 
monics. The second harmonic is suppressed 
on the order of 28 dB while the third har- 
monic is more than 34 dB down. The ef- 
ficiency of the final stage is 69% and the 
overall efficiency of the entire transmitter 
is 62%, The bulk of the total current drain 
of 2,9 A is required by the final amplifier 
-2.6 A. By choosing each of the circuit 
components very carefully, a transmitter 
evolved which uses only three transistors 
where several more stages are normally 




LI 



L2 

13 

01 

JRFC 



& TURNS B&W 3005 (i6 TURNS PER INCH, k/2" DUUtf* 
TAPPED AT 4 TUfiNS FROM COU> END, 

S TURKS NO 16, 5/16" 3iAM, [ m LDHQ 

3 TURNS NO 16 6IF1LAR WOUND ON COLO END Of L2, 

2N334, SK30OB, m«Q5 

ItipH (OHMlTE 2-144} 

Fig. 56, This simple two meter transmitter may 
be used as a driver for a larger 144 MHi trans- 
mitter or a signal source for testing receivers, 
converters and antennas. 



required. The mainstay of this transmitter 
however is the 2N3950 transistor in the 
power amplifier; this transistor can provide 
50 watts of continuous power at 50 MHz 
with a minimum power gain of 8 dB, 

Two meter driver 

The simple two meter driver shown in 
Fig, 56 is just about the minimum that is 
suitable for driving a small 144 MHz trans- 
mitter, The first stage of this VHF driver 
consists of a crystal controlled oscillator 
operating at 48 MHz; the 48 MHz output 
from die oscillator is capacitively coupled 
to the 2N1141 tripler stage tuned to 144 
MHz. The tw p o meter output of this circuit 
is quite low, but sufficient to drive a smaD 
power amplifier to a quarter watt or so, 
This circuit may also be used as a two 
meter signal source, or as a source for a 
VHF SSB mixer. 



Circuits for Test Equipment 

Signal tracer 

The signal tracer is a universally used 
unit of test equipment which may be used 
for troubleshooting and isolating defective 
stages in all types of electronic equipment 
With a suitable rf probe it may be used 
to check the operation of rf and if ampli- 
fiers; with an audio pickup probe it may 
be used as a straight through audio ampli- 



24A 



73 TRANSISTOR CIRCUITS 



5G0:3.2 




AUDIO 
PROBE .' 



.01 



GAIN 
£50* 



C l„.„j Q- ' 




m 



Fig. 57* This signal tracer provides more than adequate audio output with only 100 microvolts 
of modulated rf at the input* It may also be used for tracing audio circuits, but don't depend 
on its fidelity. All the transistors are germanium types such as the 2N404, 2NI450, 2N2953, SK3004, 
GE-2 or HEP-253; the diode In the probe is a IN34A or I N67A or similar. 



fier to check microphones and preamps and 
to detect noise and hum in amplifiers. 

The signal tracer shown in Fig* 57 uses 
a push pull output stage which produces 
more than adequate audio output to a 
miniature speaker with only 100 microvolts 
input. The output from the probe is applied 
directly to the 250 kilohm pot, which serves 
as a gain control and as a diode load when 
an rf probe is being used. The signal is 
coupled to the base of the first transistor, 
amplified, and fed to the driver stage and 
transformer coupled push pull output 

Only a very small amount of audio signal 
is necessary to operate the signal tracer 
as a straight through audio amplifier. How- 
ever, don't use it to check fidelity because 
it is designed primarily for maximum sensi- 
tivity without regard to frequency response. 

When using this signal tracer always start 
with the audio gain control turned all the 
way down because it is easy to overload 
I lie simple amplifier; the result is a highly 
distorted output signal. In some receivers 
the if probe may load the mixer plate or 
if grid. If this happens, a tone modulated 
signal should be injected at the antenna 
terminals of the receiver to obtain a usable 
output from the signal tracer. 



.002 







O+I.S 



Fig. 58. This signal injector/tracer switches from 
the injection mode to a signal tracer by simply 
plugging in a pair of high impedance magnetic 
earphones* As a tracer is works from audio up 
to 432 MHz. Transistor Q\ is a 2NI70, 2N388A, 
2NI605, SK30I t or GE-7; Q2 is a 2NI88A, 2N404, 
2N2953, SK3004 or HEP-253* 



Signal injector/tracer 

The circuit illustrated in Fig. 58 functions 
as both a signal injector and signal tracer. 
Furthermore, no switching is required; it's 
all accomplished automatically when 
the headphones are plugged in for signal 
tracing. In the inject mode the circuit is 
a clamped multivibrator with extremely nar- 
row pulses and high harmonic content. In 
fact, with this circuit, sufficient output is 
available for signal tracing from audio (750 
Hz) to well above 40 MHz. This frequency 
range is more than adequate for most re- 
quirements. 

The unit is switched to the signal tracer 
mode by simply plugging in a pair of high 
impedance magnetic headphones* In this mode 



+3V 




1.5 V 



01,02,04,06 -2W3G4, 2N2924, 2N3393, 5K3QU 
Q3 - £*404, SK3003, SKS004 

Fig, 59. This VOM range ei+ender increases the 
sensitivity of your volt-ohm-miiliammeter to 50 
millivolts full scale; full scale readings of ISO and 
500 millivolts are also provided by the range 
switch. 



73 TRANSISTOR CIRCUITS 



25A 



DiPOLE 
ANT. 




PHONES 



Fig. 60. This monitor/detector may be used for 
measuring field strength, monitoring modulation 
or finding hidden transmitters by simply attaching 
a resonant dJpole antenna at the input. Ql and 
Ql are 2N408. 2N2953, SK3004, GE-2 or HEP-253; 
Q2 is a 2NI70, 2N388A, 2NI605, SK30I1 or GE-7. 

it will detect and amplify signals from 20 
Hz to above 432 MHz. Since this circuit 
on requires about 100 microamperes, no 
on-off switch is provided. This very small 
current drain insures that the life of the 
battery will be nearly that of its shelf life. 
By using miniature components and a little 
care in layout, it is possible to mount this 
complete injector /tracer in an old penlight 
case or metal cigar tube. 

VOM range extender 

Most volt-ohm-mi II iummcters are not too 
suitable for use with transistor circuits be- 
cause their lowest voltage scales are either 
1.5 or 3 volts full scale and they are not 
sensitive enough to accurately measure the 
base to emitter voltage of a transistor which 
ma\ be 120 millivolts or so. The low volt- 
age dc preamplifier shown in Fig. 59 is 
inexpensive, stable with temperature and 
supply voltage variations yet extends the 
range of any VOM so it can be used ef- 
fectivelv in semiconductor circuit measure- 
ments. 

In this circuit transistors Ql and Q4 con- 
stitute an emitter coupled amplifier; Q5 
is an emitter follower connected so the cir- 
cuit's entire output voltage is fed back to 
Q4. Transistors Q2 and Q3 are constant cur- 
rent sources in the negative and positive 
lines respectively. These constant current 
sources reduce the sensitivity of the ampli- 
fier to voltage supply variations and result 
in substantially lower drift. To control the 
gain of the amplifier for different voltage 
ranges, a portion of thr output voltage is 
fed back to the base of transistor Q4 
through the voltage divider selected by the 



range switch. With the values shown in the 
schematic, this circuit provides gains of 3, 
10 and 30, which extend the 1.5 volt scale 
of the VOM to 500, 150 and 50 millivolts 
lull scale- 
There arc two zero controls which must 
be adjusted when using this unit; first the 
500 kilohm pot (Rl) in the base bias lead 
to transistor Ql is adjusted to zero the 
output with no input and the base isolated 
from ground. The L5k zero adjust pot (R2) 
is then adjusted for an output zero with 
the input leads shorted together. 

Monitor/detector 

The simple VHF monitor/detector illus- 
trated in Fig, 60 may be used for measur- 
ing field strength, monitoring modulation 
or even in hidden transmitter hunts. The 
frequency of use may be simply changed 
by changing the length of the dipole an- 
tenna, In some cases where the rf field is 
strong enough, a simple vertical pickup an- 
tenna will be sufficient for signal monitoring 
purposes. Furthermore, the use of this moni- 
tor/detector is not limited to the VHF 
bands; the addition of an appropriate an- 
tenna will permit its use at any frequency 
up to about 500 MHz. For lower frequencies 
where the size of the dipole antenna would 
be impractical, a simple vertical pickup 
antenna and tuned resonant circuit may be 
substituted at the input. 

1 kHz oscillator 

The simple 1 kHz oscillator shown in 
Fig. 61 is very useful for many testing de- 
vices around the shop. This circuit is simply 
a Colpitts oscillator, but the circuit values 
and feedback have been chosen for maxi- 



iOOK 



450 mn 



6 

+ t2 V 




01 - 2N2924, 2N3393, 2N356G 



Fig. 61. Simple 1000 Hi oscillator is very useful 
for testing and measurement around the shack. 
The Colpitis circuit is used with component values 
chosen for maximum stability and good waveform. 



26A 



73 TRANSISTOR CIRCUITS 



*9V 



ZQ V 






lOOiHl 
CRYSTAL 




50 



ZOO 



300 



01 -2N70S, aN27M t 2NJ9Z3, 21*3691 

Fig. 62. The 100 ItHi calibrator shown here is just 
about the simplest circuit that will provide usable 
results. For zeroing In with WWV a small padder 
capacitor may be added in series with the 100 
kHi crystal. 

mum stability along with good waveform. 
It may be used for testing speech and mod- 
ulation equipment* or even as a driver for 
a code practice oscillator. 

100 kHz crystal calibrators 

The 100 kHz crystal oscillator illustrated 
in Fig, 62 is just about as simple as you 
can build and still get a usable output. 
This circuit will provide usable harmonics 
up to about 30 MHz but it lias no pro- 
vision for zeroing in with WWV, This fea- 
ture may be added by simply placing a 
small variable padder capacitor in series 
with the 100 kHz crystal. 

The calibrator circuit shown in Fig, 63 
is only slightly more complicated than its 
counterpart in Fig, 62, but provides usable 
harmonics up to 150 MHz and has a built 
in voltage regulator. In this case the base 




R<KA). (B y iy 

5 



1600 



m 



FT! 




A 



(00 



5-80 



^70K 







m 



01 ANY NPN PLANAR SILICON TRANSISTOR 
Q2 £N2925, EN3392, 2N3565, SE4002 

ig. 63. This 100 kHz crystal calibrator is only 
slightly more complicated than the one shown 
in Fig. 62, but has a built in voltage regulator 
(Ql) and provides usable harmonics up to 150 
MHi, 



SQUARE 
WAVE 




Ql-2N70e,2Nl6l3 ( 2NZ925, SK30U 



Fig. 64, This 100 kHi crystal calibrator uses a 
crystal in the parallel mode and provides either a 
sinusoidal or square wave output. The calibrator 
may be leroed to WWV with the 4*30 pF trimmer. 

to emitter junction of an NPN silicon planar 
transistor is connected as a zener diode. 
When connected in this manner, these 
transistors provide a regulated voltage of 
approximately 11 volts. The value of the 
series dropping resistor may be determined 
by using the formula shown in the schematic. 
The 5—80 pF capacitor is for zeroing in 
with WWV, 

The 100 kHz crvstal controlled oscillator 
shown in Fig, 64 uses a low cost silicon 
transistor, and provides both a square wave 
and sine wave output with excellent fre- 
quency stability. The oscillator circuit is 
basically the Hartley type with positive feed- 
back from the collector to base through a 
phase reversal in the tapped tank circuit, 
consisting of two 240 mH chokes and a 4700 
pF silver mica capacitor. The oscillator fre- 
quency is determined by the resonant fre- 
quency of the very high Q series LC net- 
work in the feedback loop, This network is 
made up of the 4—30 pF variable capacitor 
and quartz crystal which operates in the 
parallel mode. The variable capacitor pro- 
vides a fine frequency adjustment control. 
Feedback is sufficiently large to assure 
normal circuit operation almost completely 
independent of transistor gain. The large 
amount of feedback drives the collector 
from cutoff to saturation, making a square 






73 TRANSISTOR CIRCUITS 



27A 



SO TURNS NO. 30 AWQ 
SCRAMBLE -WOUND ON 
1/4"* FOAM 





8.2k 



MODULATION 



Fig* 65. This crystal controlled oscillator provides 
very distinctive markers up to 30 MHz. The mod- 
ulation frequency is approximately 1000 Hz, but 
by changing the value of Cl it may be changed 
slightly. <? I is a 2N384, 2NI742, 2N2362 t 2 N 2084, 
TIM 10, GE-9 or HEP-2; Ql is a 2N26I3, 2N2953, 
2NI303, SK3004 r GE-2 or HEP-254. 

wave available at the output. A sine wave 
is developed across a tunable high Q tank 
and is also available at the output 

Modulated band edge marker 

The crystal controlled calibration oscilla- 
tor shown in Fig, 65 is especially useful 
for band edge marking and providing dis- 
tinctive crystal controlled markers up to 
30 MHz, To assist in identification of the 
marker, particularly at the higher frequen- 
cies where the harmonics are quite weak, 
the note may be modulated by simply turn- 
ing on the audio oscillator. The modtilatioii 
frequency of this unit is about 1000 Hz, 
but it may be changed slightly by changing 
the value of CL If the oscillator fails to 
oscillate when power is applied, reverse 
the connections on one side of the trans- 
former. At the lower frequencies the output 
of the calibrator may be coupled into the 
antenna circuit of the receiver by induc- 
tive coupling, but on 15 and 10 meters, a 
direct connection to the antenna terminals 
may be necessary to obtain sufficient out- 
put. Although this circuit is designed for a 
one MHz crystal, other crystal frequencies 



may be accommodated by changing the 
number of turns in LI. 

The two meter band edge marker illus- 
trated in Fig. 66 provides very strong har- 
monics of an 18 or 24 MHz crystal on 144 
MHz; when a sensitive converter is used 
on 432, harmonics may also be heard on 
this band* This circuit will oscillate with 
crystals throughout the 18 to 24 MHz region, 
so it may be used as a marker at almost 
any VHF frequency. The use of a 20 MHz 
crystal for example would be very useful 
for marking the lower edge of the amateur 
220 and 420 MHz bands, If a modulated 
marker is desired, the audio oscillator (Q2) 
of Fig. 65 may be coupled into the base 
of the oscillator through a 0.2 mF capacitor. 

Sweep frequency generator 

More and more hams are finding out 
that the sweep generator is one of the most 
useful test instruments to have around the 
shack. It may be used to align communica- 
tions receivers, VHF converters, to plot re- 
sponse curves and to check bandwidth. The 
circuit illustrated in Fig. 67 is a very simple 
unit that may be used at any spot fre- 
quency between 100 kHz and 60 MHz. AL 
though a three range bandswitch is shown 
in the drawing, it may be omitted if only 
one spot frequency is required (455 kHz 
for example). 

The sweep generator shown here consists 
of a single unijunction transistor sawtooth 
generator which provides the sweeping sig- 
nal for the oscilloscope and the fixed tuned 
rf oscillator. The output of the sawtooth gen- 
erator is connected across a 56 pF varicap 
in the oscillator tank which varies the fre- 
quency of the oscillator in step with the 
scope trace. The sweeping frequency may 



10k 



XTAL 

IS OH 24 
MHt 



0-9V 



I 



4.7* 




22 TURNS HO. 18 AW& 
OH 3/6" FtmM 



30 



Fig. 66. This two meter band edge marker pro- 
vides useful harmonics up to several hundred MHz 
with 18 or 24 MHi cryttals. If modulation is de- 
sired, the audio oscillator from the circuit of Fig. 
65 may be coupled into the base. Q\ is a 2NI745, 
2N2362, or HEP-2, 



28A 



73 TRANSISTOR CIRCUITS 



+ IB 




SWEEP 

RATE 
5G0h 



ftl 




/T7 /T7 /77 



SWEPT 
OUTPUT 



Fig. 67. A sweep frequency generator is a very 
handy gadget, but many times the commercial 
units are more complicated than the ham requires. 
This simple sweeper may be used at any spot 
frequency between TOO kHz and 60 MHz by sim- 
ply using the coils fisted in Table 2. By using a 
three position range switch, the three most pop- 
ular frequencies may be used, such as 455 kHz, 
1600 kHz and 10.7 MHz. Ql is a 2NI67I, 2N2I60, 
2N2646, 2N3480. or HEP-310; Q2 is a 2N74I, 
2NI747, 2N2I88, SE-9 or HEP-2. The varicap is a 
56 pF capacitance diode such as the I N955 or 
TRW V56, 

be varied between 5 and 30 sweeps per 
second with the 500k sweep rate control. 

The center frequency of the swept out- 
put is determined by the coils that are 
connected across the range switch. A list- 
ing of coils for all frequencies from 65 kHz 
to 60 MHz is listed in Table 2. When using 
this generator, always use the slowest sweep 
speed that will provide a usable trace on 
your oscilloscope. The slower the sweep 
speed, the more accurate the reproduction 
of the response curve; if the generator is 
swept at too fast a rate, the resonant cir- 
cuit being swept may ring and distort the 
curve. 



Table 2 




COILS 




Frequency 


Miller No. 


65 kHz— 140 kHz 


9007 


95 kHz —190 kHz 


9006 


ISO kHz— 300 kHz 


9005 


190 kHz— 550 kHz 


9004 


380 kHz — 1000 kHz 


9003 


700 kHz — 1,8 MHz 


v'UUii 


1,4 MHz— 3.7 MHz 


9001 


3,7 MHz— 4,7 MHz 


4508 


4.7 MHz— 59 MHz 


4507 


5.9 MHz— 7.5 MHz 


4506 


7.5 MHz— 10 MHz 


4505 


10 MHz— 14 MHz 


4504 


14 MHz— 18 MHz 


4503 


18 MHz— 23 MHz 


4502 


23 MHz— 29 MHz 


4304 


23 MHz— 36 MHz 


4303 


36 MHz— 45 MHz 


4302 


45 MHz— 60 MHz 


4301 






Sawtooth generator 

Sawtooth generators are very useful in 
many measurements and their circuitry may 
be greatly simplified by the use of field 
effect transistors. When conventional junc- 
tion transistors are used for this purpose, 
complex feedback networks and methods of 
compensation must be used to generate a 
linear voltage ramp. The output waveform 
of the sawtooth generator shown in Fig. 68 
is linear within 2% and may be adjusted 
from 1 kHz to 3 kHz by the center fre- 
quency control. The thermistor Rl provides 
temperature stability and circuit loading is 
reduced by the use of a source follower 
at the output, 

Square wave generator 

The square waves available from most 
inexpensive signal generators deteriorate 
pretty badly at the higher frequencies. In 



+ IZO 



INPUT 0— y| 



■ISO 




OUTPUT 



Fig, 68. This simple sawtooth generator is linear within 2% and may be adjusted from I kHx 
to 3 kHz with the center frequency control. Ql, Q3 t Q4 and Q6 are FETs such as the 2N38I9, 
2N3820. TIS34, MPFI05 or HEP 801; Q2 is a 2N388, 2N2926. 2N339I, SK30I I or HEP-54; Q5 is 
a 2NI67I, 2N2I6G, 2N2646, 2N3480 or HEP-310. 



73 TRANSISTOR CIRCUITS 



29A 



+ 20V 



A/Wl 




INPUT 2.} 



-6V 
ALL DIODES GENERAL PURPOSE SILICON 

Fig* 69, The square wave output of many inexpen- 
sive signal generators deteriorates quite badly at 
high frequencies, but this circuit will square them 
off again* The diodes may be any inexpensive com- 
puter type such as the IN9I4, 



addition, the output amplitude often varies 
with frequency. The addition of the simple 
circuit illustrated in Fig. 69 to the output 
of the signal generator will provide a good 
square wave output with an amplitude that 
does not vary with frequency; 

In this circuit, Ql is an inverter, while 
Q2 and the 5 kilohm amplitude control pot 
provide a variable clamp voltage for the 
output. In most cases, the necessary positive 
and negative voltages may be obtained from 
the signal generator's internal supply. The 
input potentiometer should be adjusted for 
best output waveform. Once this control is 
set, it will not change unless the signal 
generator varies significantly, Ideally, this 
control should be adjusted so that the input 
signal provides a voltage swing at the base 



of Ql from 4-3 to —5 volts. The silicon 
diode Dl provides protection for the emitter- 
base junction of Q2. Diodes D2 and D3 
prevent the clamp voltage from reverse 
biasing QL 

Capacitance meter 

The direct reading capacitance meter il- 
lustrated in Fig. 70 has four direct reading 
capacitance ranges from zero to 0.1 mF. Al- 
though electrolytic capacitors cannot be 
measured with this circuit, any type of non- 
electrolytic capacitor may be checked. In 
fact, it works as well with variable capaci- 
tors as with fixed; the meter deflection 
will follow the capacitance change as it is 
tuned. The four direct reading ranges are 
0-200 pF, 0-1000 pF, 0-0,01 mF and 0-0.1 
juF. The lowest capacitance which may be 
accurately read is 4 pF, but 2 pF may be 
estimated quite easily. 

In this circuit transistors Ql and Q2 are 
connected in a conventional free running 
multivibrator. The output from the collec- 
tor of Q2 is a constant amplitude square 
wave whose frequency is determined by the 
values of the resistors and capacitors con- 
nected across the base circuit of Ql and 
Q2, The square wave output from the col- 
lector of Q2 is coupled through the unknown 
capacitor connected across the test terminals 
to the metering circuit consisting of the 
1N34A diode, the potentiometers and the 
dc microam meter. For any given square 
wave frequency, the deflection of the meter 
will be directly proportional to the capaci- 
tance across the test terminals. For example, 
if a precision 100 pF capacitor is connected 
across the test terminals and the calibra- 
tion pot is set for full scale deflection, the 



^ ■^Jh 

p A f-wvi-o \ 

D Ql % 4 th O t 



300 

RANGES 
EA)Q-2QOpF 
fBjO-OOOpF 

+ B (D) O-O.l t# 
IE! Of F 




o 

TEST 

TERMINALS 
■O 



Fig, 70. Although this capacitance meter will not measure electrolytic capacitors, it will measure 

any other type from zero to OJ jif with reasonable accuracy. On the lower end 4 pF can be 

read accurately and 2 pF easily estimated. Transistors Ql and Q2 are 2NI68, 2NI605, 2N2926, 

SK30II or HEP-54; the meter is a 0-50 microampere unit and the range switch a Centralab PAI02K 



30A 



73 TRANSISTOR CIRCUITS 






meter will have a range from zero to 100 
pF> The response oi tins circuit is essen- 
tially linear, so 50 pF would provide half- 
scale deflection, Mo scale deflection would 
indicate 10 pf, etcetera. To change the 
range, the frequency of the multivibrator 
is changed by choosing new values of re- 
sistance and capacitance in the base circuits 
of Ql and Q2. 

Calibration of the direct reading capaci- 
tance meter requires the use of four ac- 
curately known capacitors— 0*1 ^F, 0,01 
p¥, 1000 pF and 200 pF. These capacitors 
should be verv carefully chosen because the 
accuracy of the completed meter depends 
on the tolerance of the calibration capaci- 
tors. In addition, it is essential that they 
are not leaky; if they are, the calibration 
will not be accurate. To calibrate the meter, 
set the range switch in the appropriate 
position, connect the respective calibrating 
capacitor across the test terminals, and 
adjust the calibrating potentiometer for full 
scale deflection of the meter. 

Although electrolytic capacitors cannot 
be measured on this instrument, it will 
check all other types. If a capacitor is open, 
there will be no deflection on any range. 
If it is leaky or shorted, the meter will 
deflect below zero. It is imperative that 
leaky and shorted capacitors be immediately 
disconnected from the test terminals to pre- 
vent damage to the diode and mieroamrneter. 

High impedance scope probe 

Most oscilloscope probes are unsuitable 
for use with high impedance circuits be- 
cause they severely load them down. By 
using the high input impedance characteris- 
tics of the field effect transistor, an ex- 
tremely high impedance probe may be pro- 
duced. The circuit shown in Fig. 71 uses 



*a> 



INPUT 




TO 
SCOPE 



2.2pP 



Fig. 71. This high impedance probe provides about 
1200 megohms input impedance with unity gain. 
Upper frequency equalization is provided by the 
5K pot Ql is a III 12, 2N2607, 2N4360 or TIM 1 2; 
92 is a 2N706, 2N708, 2N2926, 2N3394, or HEP-50, 



the bootstrap action of the 500 megohm 
resistor to raise the input impedance of 
the circuit to 1200 megohms. The 2 kilohni 
feedback resistor from the collector of Q2 
maintains unity gain while the 5k potentiom- 
eter provides circuit equalization. The rise 
time of this circuit is extremely fast, typically 
less than half a microsecond. In addition, 
it can handle up to two volt signals (peak 
to peak) without distortion. 

Mieroamrneter amplifier 

The sensitive mieroamrneter amplifier il- 
lustrated in Fig. 72 may be adjusted from 
approximately 2 /*A to 100 ^A full scale 
deflection each side of zero. The input im- 
pedance of this circuit is 60 kilohms at 2 
pA sensitivity and 2.5 kilohms at 100 mA 
sensitivity; total battery drain is 1.5 mA. 

In this circuit a differential amplifier with 
degenerative biasing and collector meter 
feed provide a satisfactory compromise be- 
tween sensitivity and stability. The transis- 
tors used in this circuit should be chosen 
for high current gain throughout the emitter 
current range; in addition, they should ex- 
hibit very low leakage currents. The 50 
ohm null potentiometer is used to com- 
pensate for any differences in the base- 
emitter voltage of the two transistors. The 
balance pot is used to compensate for dif- 



-0+I.5 



aiwecT 

+JMPUT 




-INPUT 



lOGfc 

BALANCE 






^WV 



soon 

SENSITIVITY 



2«7k 



S3 



PRESS TO NULL 

Fig. 72. This very sensitive mieroamrneter amplifier 
may be adjusted from 2 /iA to 100 /jlA each side 
of zero; the input impedance varies from 60K at 
2 fiA to 2,5K at 100 /*A. Transistors Ql and <?2 
are 2N930, GE-10 or HEP-50. 






73 TRANSISTOR CIRCUITS 



3IA 



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INPUT 




OUTPUT 



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Fig. 73, This logarithmic amplifier makes use of the fact that when two back to back diodes are 
driven by a current generator, they exhibit a logarithmic output of the Input signal. With the 
circuit constants shown, this amplifier follows a nearly perfect logarithmic curve over a 60 dB 
range; selected diodes will increase this to 80 dB. Q\ t Q2 and Q3 are 2N2924, SK3QI9, GE-10 
or HEP-54; DI and D2 are IN9I4. 



ferences in components and transistor cur- 
rent gain. 

The null adjustment is made with S3 
depressed, SI on and S2 on "amplifier." The 
balance is adjusted with SI on and S2 on 
""direct" Although the null is completely in- 
dependent of the balance adjustment, the 
balance must be changed each time the 
null is changed. For improved sensitivity 
a 50-0-50 jtA meter may be used instead 
of the 100 /iA movement, but at the cost 
of reduced stability. 

Logarithmic amplifier 

Logarithmic amplifiers are very useful 
for making measurements that require very 
large changes in input voltage or current 
The 60 dB logarithmic amplifier shown in 
Fig, 73 makes use of the fact that when 
two diodes are driven by a current genera- 
tor, they exhibit a logarithmic output of 
the input signal Two 1N914 diodes were 



chosen for this amplifier because they fol- 
low an almost perfect logarithmic curve over 
a 60 dB range; by selecting diodes, it is 
possible to obtain the same type of curve 
over an 80 dB spread. 

To insure that load changes are not af- 
fected by Ql, its output impedance must 
be extremely high; to cover the 60 dB range 
for example, the impedance must exceed 
100 kilohms. This is accomplished by the 
Darlington pair, Ql and Q2 and the 470 
ohm resistor in the emitter of Q2. If Q3 
is maintained in its linear range, its ac 
collector current is completely independent 
of the collector load. Hence, it presents a 
very high output impedance to the diodes; 
greater than 100,000 ohms with almost any 
silicon planar transistor. The input impedance 
of this circuit is approximately 2000 ohms, 
so it may be driven from a variety of 
sources. 

. W1DTY 



• • 



Like an extra copy of 

73 TRANSISTOR CIRCUITS? 

Bound reprints are available for $1.00 from 73 Magazine, 
Peterborough, N. H. 



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73 TRANSISTOR CIRCUITS 



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73 Magazine 



Peterborough, N.H, 03458 



The Importance of 

Being Grounded 



Ron Gunn WA6KLL 
358 Albatross Ave. 
Livermore, Calif. 94550 



Ground paths and ground connections are 
import ant at all frequencies from dc on up. 
As the frequency increases, however, the 
ground path becomes trickier and harder 
to predict. When time is spent making any 
ground path neat, direct and predictable, 
a potentially serious source of trouble in the 
circuit is eliminated. 

Have you ever had if all over the shack 
or a power amplifier or if strip just not 
act right? The trouble could be lack of a 
secure, solid, short rf return path to the 
cathode or emitter of the stage. An example 
of the need for a good return path is prob- 
ably a few feet away as you read this. 
Notice the cord to the lamp you are prob- 
ably reading by. It contains two wires, one 
to supply current to the lamp, and the other 
to allow the current to return thru the 
transformer* Notice (or be informed!) that 
both wires are the same size, correctly in- 
ferring that both are of equal importance. 
Remove one of the wires and no light! So 
watch your grounds and regard them as 
equal in importance with the coils, capaci- 
tors and other components of your rf cir- 
cuits. 

An unpredictable ground on a power 
amplifier can produce rf all over the shack. 
To see why, let's remind ourselves of a few 
things about radio frequency energy, rf 
current always takes the path of least re- 
sistance and inductance. If a less inductive 
route exists around a long path than thru 
a shorter path broken by a bolted joint or 
partition, then the current will go the long 
way. Partitions are harmful to the return 
path because when they are tight, rf cu- 
rents cannot go around them, nor can they 
penetrate thru to the other side- A phenom- 
enon called skin effect causes rf currents 
to run only along the surface of a conduc- 
tor, penetrating less than 10 mils at even 



the lowest amateur frequency in aluminum, 
even less in copper. 

Additional things to remember are that 
bolted joints are always Iossier than a 
straight plate, and if energy does not like 
to go around sharp corners or around edges 
of material to get where it's going. 

The way some power amplifiers are built, 
it's a wonder that they are as stable or as 
interference free as they are. Imagine the 
rf return current from a high power ampli- 
fier having to sneak along the chassis, once 
it leaves the output connector, going under 
partitions and across bolted joints to get 
back to the PA cathode. More than a bare 
minimum of it is going to go around, travel- 
ling along the outer surface of the rig. 
When Lliis happens, the chassis radiates 
and sometimes develops an appreciable dif- 
ference of potential from surrounding and 
perhaps better grounded metallic objects. 
Presto— a rig that produces rf in the shack. 

What does one do about all of this? Sim- 
ply provide a neat, direct and predictable 
ground for the stage. A flat piece of cop- 
per or other conductor run directly from 
the output connector to the cathode is best, 
a heavy wire can be used to get by on. 

If no reasonably thin copper strap is 
available a favorite (and enjoyable) stunt 
is to cut a beer can at the seam (must be 
emptied first) and scrape away the lining 
where it is desired to solder. The half quart 
size is (smack) best. Aluminum is less sat- 
isfactory to use as all connections are nor- 
mally only bolted down and a connection 
to the tube base and the cathode pin di- 
rectly from the nearest point of the strip 
is not easy to obtain. 

The rf current will flow along one side 
of this strip as the edge tends to restrict 
current flow to the surface upon which it 
was launched. When tying components to 



98 



73 MAGAZINE 



the strip, use the same side for best results, 
particularly at the higher amateur frequen- 
cies. 

To complete the job, tie all bypasses 
and tuning capacitors directly to the strip, 
or run a large lead directly to them. Don't 
depend on a shaft bushing to provide the 
return path for these critical rf components 
as this path may be longer than the one 
discussed earlier that went from the output 
connector to the cathode. Most components 
that are adjusted in operating the gear end 
up bolted thru the front panel and really 
deserve a much better return path to the 
cathode than they usually end up with. 

As the frequency of operation increases, 
the effects discussed will become more pro- 
nounced. Currents will travel ever closer 
to the surface and direct ground paths will 
become more important They are already 
important at even the lowest amateur fre- 
quency. 

Let's review the important points now that 
the groundwork (!) has been laid: 

1. Use a neat, direct, predictable ground 
plate from output or load back to the 
cathode. 

2. Avoid bolted joints in the return path, 

3. Avoid going under tight partitions. 

4. Tie all bypasses and tuning capacitor 
frames back to the ground plate. 

He member that: 

1. rf currents do not penetrate very deep 
but flow along the surface of a conductor. 

2. rf currents will not go thru a plate, 

3. rf curents tend to stay on the suface 
upon which they are launched. 

rf power amplifiers are not the only 
ihinps that require good pround returns. 
That lias been the main topic here, but the 
ideas are 100% applicable when construct- 
ing stable drivers, oscillators, rf and if 
amplifiers, and even audio amplifiers. They 
all deserve the same treatment: a neat, 
direct and predictable cathode return path. 

The essential thought here is that the 
builder of any piece of gear should sit 
down and trace out the ground return path 



of every stage. Where a direct path from 
one cathode or emitter to the next is not 
obvious, continuous and relatively unim- 
peded—put it in yourself. 

The results can be quite dramatic. A 
thousand watt class C amplifier that was 
recently designed and put into service here 
at WA6KLL was constructed using a 3" 
wide copper strip down the front panel 
and direct]\ back to the cathodes of the 
two 813's, All bypasses from the tube socket 
were tied directly to this strip. The output 
connector and the tuning capacitors all 
mount thru the strip and the front panel 
and are strapped to the strip. The shielding 
to the compartment consists of aluminum 
screen with the frame secured bv catches 
spaced at a quite wide 7 inch interval* 
There is no radiation of energy from the 
cabinet even with this minimal shielding, 
A portable TV ten feet away using an in- 
door antenna in our fringe area is unaf- 
fected when the transmitter is keyed, even 
on channel 2 (50 miles over hills). The 
ground return may not be the whole answer, 
but nobody's touching itl 

The problem with specifying good return 
paths on circuits is that the schematic re- 
mains the same. If you are homebrewing 
from someone else's schematic, you had 
better know at least as much about the 
ground return problem as the designer or 
problems may occur. It is the rare construc- 
tion article that delves far enough into 
"well-known, fundamental" concepts as 
grounding. Usually the requirement for con- 
sidering the returns is your responsibility 
as the builder. Failure to consider the 
ground path (since it is not particularly 
specified on most schematics) may be the 
cause of a perfect circuit that just doesn't 
work well for some reason. 

If you ever have any doubt about the 
path return currents must take in any stage, 
provide one yourself that you can depend 
on. The results will often be well worth the 

trouble. 

, . . WA6KLL 




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Gus: 



Part 21 



The trip to Mombasa was very enjoyable, 
plenty of good food and plenty of good rest 
No/MM this time* the ship had a new wire- 
less operator who knew nothing about ham 
radio, pins the fact he was new on the job 
and did not want to "take a chance", even 
tho I were willing and ready to get going 
from the ship. The rest did me plenty of good 
and I had time to get all my logs ready to 
be mailed to Ack upon my arrival in Mom- 
basa, Good old Leny 5Z4GT and 5Z4AA 
met me at the docks when the ship arrived. 
5Z4AA was way up in the Police Dept and 
a nod from him to Customs did the trick, 
and in a few moments all my equipment 
was in Leny's car and away to my hotel 
we went I spent only one or two days in 
Mombasa, did a little shopping down at the 
local market place— where all those carv- 
ings are— REMEMBER! I had nothing to 
trade them this time so I had to do it the 
hard way— by bargaining a few hours, even 
though I spent only about maybe $10.00 I 
got a big armfull of some FB carvings, I 
had found out how to "bargain" with these 
people while "drinking their Cokes", and I 
still think they love it, A few even remem- 
bered me being there before— One referred 
to me as that big business man from Amer- 
ica, They never say the U.S. A.— You know 
they call us Americans, this is true in every 
country I have ever visited Not just Kenya. 
They were referring to my big business 
deal** that I had with them a few years 
previously when I traded all that "genuine 



plastic" jewelry to them, THEY WANTED 
TO KNOW DID I BRING SOME MORE! 1 1 
They all thought I was a "Big Deal" 
fellow. 

The evening's train was caught for Nai- 
robi, you know it only makes that trip at 
night, I guess it's too hot to be made in the 
daytime, plus the fact at night they sell you 
a "sleeper coach ticket" and that puts a 
few more pounds in someone's pocket I sup- 
pose. Arriving back in Nairobi was sort of 
like coming back home, all the sights was 
familiar to me, even the taxi drivers with 
those LONG earlobes with the hole in 
them and the tall, Fez-sort-of- looking hats 
they wear. Good old George 5Z4AQ met 
me at the train and away to his home we 
went, outside the city limits of Nairobi a 
few miles. Right besides hole Nr. 5 of a 
golf course which had that sign near hole 
Nr. 5, saying, '^beware of the lions near 
hole 5" And don't think this sign is there 
just to be funny— there are LIONS around 
there, George said one night he saw five of 
them walking across his lawn. There are 
also hyenas there, George put a piece of 
meat on his front steps one night and about 
midnight there was that laughing hyena 
sound out on the FRONT PORCH, and there 
they were fighting over that chunk of meat 
George at that time was working with 
Kenya Television near Nairobi and he had 
the usual "understudy" following him all 
over the place when he was on the job. His 



73 MAGAZINE 



MEAT AND POTATOES AND 
SOMETHING CALLED VALUE 

I am always on the lookout for electronic 
components or assemblies which possess po- 
tential ham value, I have also been interested 
in any item which makes it possible for more 
hams to enjoy sideband. You can, therefore, 
understand how happy I was when on a re- 
cent western trip I found one lot of 225 watt 
core power transformers and in another area 
a batch of computer grade electrolytic con- 
densers. Immediately, I felt that we could 
put out a darned good universal transceiver 
power supply and when I got back, the boys 
in the shop confirmed this. 

I say universal because with two of these 
power transformers and two 500 mil chokes, 
12 diodes, assorted resistors and other com- 
ponents, we were able to make up a supply 
which met the requirements of the latest 
Swan, Collins, Drake, Hallicrafters, Heath, 
and National transceivers. Talk about value! 
We can offer this complete assortment of 
parts including a 16 gauge steel chassis and 
bottom plate, a good PM speaker and mating 
plugs for your particular transceiver for just 
$50, The transformers in this set weigh 17 
lbs. and altogether the completed supply will 
weigh close to 40 lbs. This is what I call 
meat and potatoes. The filtering is excellent; 
the regulation is extremely good, and we 
have schematics and a printed story to be 
supplied with each kit, giving detailed infor- 




mation as to how to make the connections for 
your rig. You will have to tell us what model 
you own. 

This is what the power supply w T ill do: 

800-1000 V at up to 400 mils on peak 

285-320 V at up to 300 mils 

bias of up to 125V at 100 mils 

12V DC at 1 ampere 

12,6V AC at 6.5 amps 

Remember, this is an assembly of parts. 

We do not furnish a drilled chassis; we do 
not furnish the hardware; we do not furnish 
the solder and the wire but literally every- 
thing else is supplied. 

Please allow for 45 lbs, shipping weight or 
otherwise be prepared to accept Railway Ex- 
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MARCH 1967 



101 



mm 



understudy I think he said was "Kyuku,** 
one of the natives of Kenya, George sud- 
denly has left 5Z4 land you know for ZSti 
land so I guess that 5Z4 fellow has stepped 
into his job. Boy I bet that Nairobi T,V. is 
not on the air 100% of the time. I guess 
being from ZS land (that's where George 
is from you know) is sort of tough on a 
I fllovv in 5Z4 land. Must be getting sort of 
tough all around now because Leny 5Z4GT, 
I understand will be leaving, I think next 
year for U.K. Sort of looks like all of them 
are leaving, Robbie is still there, had a QSO 
with Wayne Green W2NSD/1 from 5Z4ERR 
a few weeks ago. I wonder if he will be 
leaving one of these days? Maybe the day 
will come when 5Z4 will become a rare one? 
Maybe someone will have to go there to give 
the boys a new one some time. George told 
told me ALL ABOUT the situation when I 
were there, a very interesting story too. 
Time to depart for Ruanda and Burundi 
soon arrived and George took me down to 
catch the train. George's wife is incidently 
a good cook, fellows, hunt them up if you 
happen to get down to ZS6 land sometime, 
Tell em, *Gus sent me\ 

The trip to Lake Victoria was only a few 
hours, I saw the ''Great Rift Valley" from 
the train. In fact the train goes thru the 
Rilt VlI , a sunken portion of the country 
quite a number of miles across in this por- 
tion of Africa* I understand this Rift Valley 
extends from down near Northern Rhodesia 
all the way up thru Africa, across Asia 
Minor across Iran maybe even into Russia. 
Maybe part of it is in Eastern Turkey where 
they had the big earthquake a little while 
back, It could be seen very easily from the 
train. The land had sunken down some hun- 
dreds of feet I would estimate. 

Arriving in Kismu on Lake Victoria the 
weather was extremely hot. Loading the 
Lake steamer took about four hours it 
seemed to me. The boat was full mostly of 
natives, some returning to their homes from 
working in Nairobi or maybe Nakuru or 
maybe even Mombasa. Quite a number of 
Europeans in their White suits also went on 
board. The steamer headed across the lake 
for Kampala, Ugunda. Taking about one 
half the day to get there. The ship was close 
to the land quite a while and many croco- 
diles were seen, even a few hippos and even 
some dozen or so wild water buffalos— 
thats those "mean ones* 1 that vou don't 
monkey around with at all Those are the 



ones you had better "kill" if you shoot at 
them or you are in for a lots of trouble, I 
was glad we were on a ship and they some 
distance away, even then they gave the boat 
a "mean look". The crocodiles just sank 
below the water and disappeared from sight 
Upon landing in Kampala everyone went 
ashore and we were taken to a nearby wa- 
ter-front hotel and told to have a drink on 
the house, some of us wandered out and 
walked around town, I picked up a few 
carvings and some native-made items. The 
weather w as too hot for me to walk all over 
so I headed back to the hotel/restaurant 
Stayed there some three or four more hours 
until we were told to go back to the ship. 
The little whistle tooted a few times and 
we were away for the Sourthern part of 
Lake Victoria. The ship docked at Mwanza 
which is in Tanganyaki. This was where I 
was to meet 9U5JH from Ruanda, He was to 
arrive late that afternoon. I was met at the 
docks by a VQ3 fellow from either Kanama 
or Shinyanga where he was managing a 
diamond or gold mine. He was originally 
from ZS land so I am quite sure he is not 
in Tanganyake at this time. He drove me 
in his car all over the little town and we 
had a very fine meal at a local hotel-restau 
rant and chatted until late in the afternoon 
when John, 9U5JH arrived in his 1959 
Chevrolet which he had driven all the way 
from Burunda, All three of US had a big 
"eye ball QSO" for an hour or two, the VQ3 
chap departed for his home QTH, John 
gassed up filling a few five gallon cans full 
of gasoline for the trip back to Burunda 
across unchartered roads with no filling sta- 
tions and no signs of civilization at all were 
seen bv us as we drove to 9U5 land that 
night. All THREE SPARE tires was careful- 
ly checked, two spare cans of water was 
filled, a few extra quarts of oil were bought, 
and awav for 9U5— Burunda we went Now 
don't jZet the idea that there is an "inter- 
state 1 highway between these two places, 
don't f.*et the idea that it's even a paved 
road, or you will be completely wrong. This 
auto trip was nearly what you might call 
a safari. We were packed for a safari I 
would say. We had everything a safari has 
except "guns". Later on I sure wish we had 
a gun or two with us. This was going to be 
another of those trips I was to remember 
all mv davs. Dirt roads all the wav, not one 
single road sign and many many roads turn- 
ing off to the right and left. All of tliom 



102 



73 MAGAZINE 



looking right to me, A few times we chose 
the road by refer ing to our compass. OH 
YES we took quite a few wrong roads. John 
could speak Swahili so we had no trouble 
getting back on the right road, but if you 
don't speak Swahili— Brother don't you dare 
make this trip or you will end up staying 
there all the rest of your life* No one we 
i net all the way spoke ONE WORD OF 
ENGLISH, and Brother this can get rough. 
Most of the natives were more or less 
liiendly, but a number of them looked 
downright "mean" to me, not a sign of a 
smile could be seen on their faces* When 
you leave the town limits of Mwanza and 
arc out on that road a few hours, you know 
you are in "deep Africa", you smell it, you 
see it, you hear it, you hear in the distance 
the beating drums (this trip was an all 
night affair you know), even the stars sort 
of have that African look, the trees are a 
dead give away. You remember seeing those 
"flat top" trees in African movies? Well 
they are here, and I mean all over the place. 
Those darn beating drums are what got to 
me more than anything else, some sounded 
like they were saying bong, bong, bong 
diddy bong, others sounded like bang, bang 
space bang bang bang, All had a different 
sound and were beat in a different sound- 
ing way; I was thinking to myself something 
like this— "I wonder what those things are 
saying to each other". Because some of them 
were most certainly answering the other 
drummer's CQ. I wonder when they sign 
off do they have a certain thing that says 
73? Those jungle sounds were sometimes 
frightening, at times smooth, and sort of 
soothing. I had been in the African jungle 
before a number of times between Mombasa 
and Nairobi, Kenya and twice between Nai- 
robi and Dar es Salaam, Tanganyaki, but 
I was in a bus along with about 25 or so 
people all the time and on at least a 
"marked road". You might say the other 
roads were roads that were traveled on by a 
good number of cars every day. But this 
was now a real "back country" road and 
lead us straight in the middle of real wild 
country— a part incident ly where Dr. Liv- 
ingston went for supplies to Dar es Salaam 
and very definitely a portion was used by 
Stanley when he was hunting Dr. Living- 
ston. This was an all night trip and half of 
the next day. You know wild animals are 
daytime sleepers and roam around at night. 
So doggoned many different kinds of ani- 



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We also carry a complete stock of Hy-Gain 
antennas, new and used, All materials for any 
antenna installation. Write for information and 
prices* 

ANTENNA MART 

Box 7 Rippey, Iowa 50235 



MARCH 1967 



103 






VANGUARD 
MODEL 501 
Mitf* in USA 




S279.95 

SHIPPING COLLECT 
COMPLETE WITH LENS 

SUB MINIATURE SOLID STATE 

TV CAMERA 

rOR CLOSED CIRCUIT OR AMATEUR TV 

THE VANGUARD 501 is a completely automatic 
closed circuit television camera capable of transmit- 
ting sharp, clear, live pictures to one or more TV sets 
of your choice via a low-cost antenna cable (RG 59U) 
up to a distance of 1000 ft without the need for ao 
cessorres or modifications on the TV sets. The range 
can be extended indefinitely by using line amplifiers 
at repeated intervals or by using radio transmitters 
where regulations permit, ' 

There are hundreds of practical uses in business, 
home, school, etc- for any purpose that requires you 
or anyone chosen to observe anything taking place 
anywhere the camera is placed* Designed for contin- 
uous unattended operation, the all-transistor circuitry 
of the 501 consumes only 7 watts of power. 

SPECIFICATIONS: 

• Measures 2W X 4" x 7" (excluding lens and connectors). 

• Weighs 31/2 lbs. 

• Operates on 100-130 volts SO or 60 cycles, 7 watts. 

• Tested at 10° to I25 a F. 

• Advanced circuitry utilizing 35 semi-conductors most of 
which ere silicon, 

• Freld effect input circuit for minimum video noise. 

• Resolution guaranteed to exceed standards set by 525 
line TV receivers. 

• RF output 30,000 microvolts adjustable for channels 2 
to 6. 

• Video output 1.5V p-p composite with standard nega- 
tive sync (random interlace), 

• Viewable pictures obtainable with illumination as low 
as 1 ft. candle. 

• V id icon controlled light compensation; 150/1. 

• Adjustable iris on tens enables use in bright sunlight. 

• New long life, sub-miniature v id icon with spectral re* 
sponse similar to Type 77 35 A. 

e Electronically regulated power supply and thermally 
compensated circuits eliminate change in picture quality 
when line voltage and temperature fluctuate. 

• All parts guaranteed for 1 year [except for open fila- 
ment on vidrcon or breakage)* 

• Fa* », low*co&r service always available from our factory 
in Mollis, NY. 

Pre -set adjustable controls include the fallowing : Video gain, 
video compensation, pedestal level, target voltage, beam voltage, 
beam alignment, electrical focus, horizontal frequency, horizontal 
size, vertical frequency, vertical size, vertical linearity, modula- 
tion and RF frequency output. 

Send your order direct fo our factory 

VANGUARD LABS 

196-23 Jamaica Ave. Dept S RoHis, NX 11423 



ma Is was seen it's hard to remember them 
all, John (9U5JH) had along in his car a 
head light sealed beam light mounted on 
the end of a short handle with the end of 
its cord a plug that we plugged into the 
cigarette lighter on the dasboard of his 
car. When we saw a pair of eyes in the 
distance I would snap on the light and zero 
in on them and keep the light in their eyes 
until they disappeared into the jungle. Most 
of them did not try to evade staying in the 
light Many many lions, big baboons, ante- 
lopes, zebras, rhinos, elephants and best ol 
all quite a few big beautiful leopards set- 
ting up on rocks beside the road ready to 
pounce on anything that happened to pass 
their way. When we passed them you can 
bet the windows were rolled up. We did 
not want a leopard jumping in our car. 
These rascals usually would just set there 
watching the car as it passed. A few times 
we pulled up and stopped parallel to them 
and I kept the light in their eyes and had 
a good chance to look them all over, Boy t 
if we only had a gun along with us, Peggy 
would have had a few leopards skins to- 
wards a leapord skin coat. It would have 
been so easy to shoot them smack between 
the eyes and not even leave a bullet hole in 
their skin. But all we could do was just 
"look" at them from the safety of our car. 

Lions: this was their hunting grounds, 
they were to be seen at least every half 
hour. We would see from one to three or 
four, I mean right beside the road. They 
were like the leopards— not afraid of any- 
thing. The most numerous of all animals 
was those hyenas. Many other animals were 
seen. Many of them, not even John knew 
their name, some looked sort of like our 
American racoons and opossoms. My flash 
no pictures was taken I am sorry to say. 
Even a few very large snakes crawled across 
the road, probably pythons, This was the 
real African jungle and I was a little bit 
on the edge everytime we stopped the car t 
wondering if it would start again O.K. My 
only regret was that it was a fast trip with- 
out many stops along the way. After the 
all-night trip from Mwanza and driving all 
the next morning we arrived at Kitega, 
Burundi and drove a few miles from town 
to the home QTH of 9U5JH which was at a 
missionary settlement on top of one of those 
hundreds of little hills that you see in 
Burundi. As a rule the Eruopeans build their 
homes on top of these hills and the natives 



build theirs down in the valleys between 
the hills. The natives lived in typical 
thatched huts with many many banana trees 
all around their settlements. I asked John 
why all the banana trees, thinking they ex- 
ported bananas, and he said they made 
Kinana wine from the fruit. He said this 
banana wine was very powerful stuff and 
that great quantities of it was consumed by 
the natives. We also saw quite a few tea 
plantations here and there usually on the 
side of the lulls. The temperature was not 
too bad on top of those little hills. Usually 
a slow breeze bleu during the daytime and 
at night it was very pleasant, late at night 
getting a little chilly, John had up a real 
nice 20-meter quad, maybe it was also 10 
and 15 because it was of the center spider 
construction, His equipment was cleared 
from the operating table and mine was 
placed there and tuned up. I was on the 
air as 9U5JH, the band stayed open until 
about 3 AM and was open to everybody 
all at the same time* All my "Gus watchers" 
were in the pile-up and I had a ball with 
FB signal reports from everywhere. Nearly 
everyone saying I was a new country for 
them, which I doubt since John had always 
been quite active and many other 9U5*s 
from Burundi had been on for many years. 
I am a firm believer that, "if you are the 
rarest thing on the air, you automatically 
become DX to everyone everywhere, and 
they will join in the pack just to be working 
DX. Of course this suited me FB because 
the bigger the pile the better I like it. A 
DXpcdition wants big business, that's the 
reason there are DXpeditions you know. 
John filled up the coffee pot and told me 
how to heat up the coffee. Milk and sugar 
was on hand and everytime I got a little 
sleepy, to the coffee pot I went. John had a 
nice wife and she was a good cook so there 
was always plenty of good food there. My 
stay with John was one of those good ones. 
The kind you are always looking for when 
you get away from home. John told me 
many stories about what has happened there 
since he had arrived, lots of good ones about 
lions getting into native huts, gobbling up a 
few of them, then their lion hunt to get 
the "man eater". You can be sure these 
things do happen in deep Africa, they right 
now have lion trouble in some of the out 
laving places I am sure. That's it for now 
fellows, MORE NEXT MONTH. 

, . . W4BPD 



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voltage regulation, 6 to 12 volts posi- 
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196-23 Jamaica Ave. Hollis, N. Y. 11423 



MARCH 1967 



I OS 



Jim FiskWlDTY 
RFD I, Box 138 
Rindge. N. H. 03461 



Waters Dummy Load and Wattmeter 



The new dummv loads from Waters 
Manufacturing down in Wax land, Massa- 
chusetts, nicelv fill the amateur need for a 
dummy load and/or wattmeter that he can 
depend upon. The two models are basically 
the same load, but the Model 374 has a built 
in wattmeter while the Model 384 does not. 
These loads consists of a structured mono- 
lithic 52 ohm non-inductive resistance unit 
designed to present a constant impedance of 
52 ohms over the frequency range from dc 
to 230 MHz. To provide adequate cooling 
when large amounts of power are dissipated 
by the resistor, it is sealed into a steel con- 
tainer filled with oil; a thermostat is also 
sealed into the container as an indicator of 
maximum safe operating temperature. 

Since the impedance of a load of this type 
is dictated solely by the physical geometry 
of the load resistor, once it is sealed into 
the can, it cannot be adjusted. However, the 
manufacturer states that the maximum 
SWR is less than 1.3:1 from dc to 230 MHz, 



and tests with a commercial SWR bridge 
bear this out. The load is somewhat flatter 
(closer to 52 ohms resistive) on the high 
frequency bands up to 30 MHz llian on the 
VHF bauds, but even at 230 MHz the mea- 
sured SWR was less than 1.3:1. 

The two loads appear to be identical ex- 
cept that the 374 Dummy Load— Wattme- 
ter has a built in rf wattmeter. This watt- 
meter consists of a semiconductor rectifier 
and filter network which furnishes a dc volt- 
age to the meter movement from the rf 
voltage across the load. The dc voltage is 
connected to the meter through four resis- 
tive attenuators to provide full scale read- 
ings of 15, 50, 300 and 1500 watts. This 
instrument is calibrated at the factory with 
a precision low frequency wattmeter and 
the guaranteed accuracy from 2 to 30 MHz 
is ± 5% of the full scale 4 reading on each 
range. This means that on the 1500 watt 
range the reading is ± 556 of 1500 or ± 75 
watts. The accuracy from 30 MHz to 230 









DUMMY iOAD 

scr«*fti 'taw***""* 
tt*fi ****** ■"*■ ^^ ' 

viwt 



avri th*" 1 * 1 



p«i* TO ' 



"JtlWQ ftt< " 



1 0b 



73 MAGAZINE 



MHz is not stated by the manufacturer be- 
cause the power readings above 30 MHz 
will be somewhat higher than predicted. 
However; the 374 may be used as a relative 
power indicator up to 450 MHz; above 230 
MHz the power input should not exceed 250 
watts. 

One very nice feature of the wattmeter is 
that it is possible to run a quick check on 
the calibration with normal 120 Vac, 60 Hz, 
line voltage, Immediately after calibration, 
the technicians down at Waters make a note 
of the reading obtained on the 50 watt scale 
when 120 Vac is applied to the input ter- 
minals of the model 374 and record it on the 
rear panel of the instrument. No attempt 
should be made to correlate actual power 
levels at 60 Hz with the wattmeter readings, 
because the circuit is not compensated for 
this frequency, but it does give the ham out 
in the field an opportunity to check the cali- 
bration. 

These loads are very useful for loading 
your transmitter without radiating a signal 
and for measuring the power output of your 
transmitter. The Model 384 does not have 
a built in wattmeter, but it may be used 
with the Waters 369 Reflectometer to pro- 
vide accurate, direct measurements of rf 
power. If your antenna is very closely 
matched to 52 ohms, your transmitter may 
be loaded into the dummy load and then 
switched to the antenna with no changes 
in final amplifier tuning. If a coaxial switch 
is used to switch the transmission line from 
load to antenna, make sure you turn off 
the transmitter when switching. 

The wattmeter is also useful to checking 
the loss of coaxial transmission lines and 



Waters? Model 384 Dummy Load 

Specif f cations 



Frequency rangre 
Load impedance; 
Power rating: 



Input connector : 



Power It e<| ti i rem euts : 



Weight: 
Prices 



DC to 230 MH^ 
52 ohms nominal. 
1500 watts (inter- 
mittent). (Maximum 
inner case tempera- 
ture of 220° is 
reached in 4 to 6 
minutes at 1500 
watts input). 
Hermetically sealed 
SO-239 UHP mates 
with standard UHF 
PL-25B plug*, 
120 Vac, 60 Hz (for 
over temperature 
warning: light)* 

1Z pounds, 
$65,00 



rr 



Model 374 Dummy Load - Wattmeter 

S pe ei f ica t ion h 

Same as for the Model 3&4 above except 

as follows: 

Wattmeter ranges* 0-15, 0-50, 0-300, 0-1500 

watts. 

Accuracy: rh 5% of full scale 

value from 2 to 30 
MHz. May be used as 
a power indicator 
from 30 MHz to 230 
MHz without state- 
ment of accuracy* 

Price t $135.00 



for checking and adjusting SWR bridges. If 
you suspect that old World War II coax 
you're using is lossy, a quick check on the 
Waters 374 will confirm ( or deny ) it, 

Once you have one of these units in your 
shack, whether it's the 374 Dummy Load- 
Wattmeter or the 384 Dummy Load, you'll 
wonder what you did before you got it. Be- 
sides, all your ham buddies in town will be 
over to borrow it! • . . W1DTY 






WTW News 

We've printed up a small WTW countries 
list which you can use to check off each 
WTW country as you work it. It has a place 
for the date of each QSO and a place to 
check when you receive the QSL. Please 
send a self-addressed business envelope for 
your copy. 

WTW Awards Issued 



SSB WTW-200 
SSB WTW- 100 



1. Bob Wagner W5KUC 

1. Gay Milius W4NJF 

2. Bob Wagner W5KUC 

3. A. A. Hopple W3DJZ 

4. Bob Gilson W4CCB 



CW WTW- 100 



5. Jim Lawson WA2SFP 

6. Joe Butler K6CAZ 

7. Warren Johnson 
W0NGF 

8. Ted Marks WA2FQG 

9. Lew Papp W3MAC 

1 0. George Banta K1SHN 

11. Don Redman K8IKB 

12. Paul Friebertshauser 
W6YMV 

13. Jay Chesler W1SEB 

1. Vic Ulrich WA2DIG 

2. James Resler W8EVZ 

3. Dan Redman K8IKB 



MARCH 1967 



107 




I i I M 1 1 ] I f 1 1 f I r 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 L£ 

Master Code S 

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| TELEPLEX METHOD Code In- = 

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skill. Shaky speeds of a few words per minute — 

may be gained in most any haphazard, hit-or- ™ 

miss system. Professional skill will be gained ^ 

only from professional training. Brochure 7-5 is ^ 

free — it gives you the facts. ~ 

1 TELEPLEX COMPANY | 

= 739 Kazmir Court, Modesto, CaL 95351 = 
niMIIIIIIIIIIIIIIUllNlllllllllMMIIIIIIMIIIIMIIIMIIlF 



Questionnaire 




What with new breakthroughs in semiconduc- 
tors, two meter moon bounce, Don Miller, lasers 
and Incentive licensings, we want to know your 
interests. Please clip l tear, rend, or in some way 
remove this questionnaire (or even just copy it) 
and let us know post haste your interests. 



1. Are you licensed? yes no_ 



2. Do you work in electronics? yes. . no 

3. How lo have you been licensed? 0-1 
year : 1-5 ; 5-up 

4. Class license? Nov : Tech _; &eru ; 



Cond, 



Adv ; Extra 



5, Do you own an SSB transceiver- yes 

no 

6, About how many hours a week do you de- 
vote to amateur radio? . 

Please indicate the approximate percentage 
of your time you spend on the following: 

7, Bands used: 160M 80M 40M 

20M ISM I0M 6M 2M 



220MHr 



43 2 M Hi. 



oth 



er. 



8. Modes used: S5B. AM — _ 

CW RTTY TV, FAX 



Mobile. 
_ FM. 



NBFM 



other 



9, Ham activity: Rag chewing ; DX ; 

Traffic ; Construction .; Contests. : 

other 

10. Do you belong to an amateur radio club- 
yes no 

11. How much do you expect to spend on ama- 
teur radio in the next year? 

12. What major items are you considering pur- 
chasing? 

13. You like to buifd, you say? What construc- 
tion articles would you particularly like to 
see? 



A Hint for the TR-4 

Occasionally a TR-4 transceiver owner 
lives near a high power broadcast station 
that concentrates an antenna pattern in his 
direction. The result maybe an annoying 
signal appearing on one of the ham bands. 

To eliminate the trouble it must be de- 
termined if the interfering signal is the 
fundamental or a harmonic of the station. 
Generally this is very easy to do. If the 
signal comes in loud and clear with no dis- 
tortion it can possibly be the fundamental. 
II there is distortion or garble die signal is 
a harmonic because every time the frequency 
doubles, the audio signal components double 
and the station sounds distroted. The fre- 
quency of the incoming signal has to be 
determined so that a trap can be installed 
in the transceiver. 

In my particular case I was troubled by 
XERB at 1090 kHz coming in on the twenty- 
meter ham band. It was found that this sig- 
nal could be almost eliminated by using a 
series tuned trap across the neutralizing ca- 

icitor in the driver grid circuit to trap out 
the interfering signal. 

For this particular station the fundament- 
al was the culprit and a trap was made by 
from a 37-250 pF trimmer capacitor and 
0.1 mH if choke in series across a 865 pF 
capacitor (C-43) located in the grid circuit 
of the driver. 

After the trap is installed, listen to the 
station and tune the trimmer for a minimum 
signal If the trimmer closes without tuning 
through a minimum connect a 100 pF ca- 
pacitor across the trimmer. The choke in 
series with the trimmer resonants at 1090 
kHz which does the trick. Frequencies not 
in the broadcast band will take different 
values which would have to be calculated 
for the interfering frequency. 

Essentially what we have done is to trap 
out the interfering signal at the grid of the 
6EA8 mixer tube. There is no reason why 
other transceivers using the* final amplifier 
grid coil as the antenna coil coupled to the 
mixer, and having similar interference prob- 
lems, could not be fixed by the same method. 

. . . Ed Marriner W6BLZ 



PLEASE INCLUDE YOUR ZIP CODE 
WHEN YOU WRITE 73, 



108 



73 MAGAZINE 




AMECO 



NUVISTOR LowTioisE PREAMPLIFIER 




Ideal for 
operation 



For 27 (CB), 28, 50, 144 or 220 MC. (Also available 
for 150-170 MCS) 

Add this Ameco Nuvistor Preamplifier to your re- 
ceiver (or converter) to improve the sensitivity and 
noise figure. Two tuned circuits also improve rejec- 
tion of image and spurious frequencies. Compact, 
easily connected and low power requirements, wired 
and tested with tube. 

1 Model PV 27 $11.95 

Models PV 28, 50, 144 & 220 $13.95 

Write for details on 150-170 mcs and others. 

improving performance of surplus FM Two-Way equipment for "NET" 
on the 2 and 6 meter bands. 




MANUFACTURERS OF FM AND AM TWO-WAY RADIO, SSB AND ISB 
COMMUNICATIONS, CONTROLATOR FUEL CONTROL AND DATA EQUIP- 
MENT, AMECO* HAM, CB AND SHORT WAVE LISTENING EQUIPMENT. 



AMECO EQUIPMENT CORP. 

A SUBSIDIARY OF AEROTRON, INC. ■ P. 0. BOX 6527 ■ RALEIGH, N. C. 27608 



You won't be able to put it down! 

We should giv* fair warning to those who ordtx 
this new book from the Radio Society of Great 
Britain. One* you pick H up. you won't bo able 
to eat, sleep, talk or watch TV unfit you've read 
H all. It'i a fascinating, densely-packed, 100- 
page book full of every Imaginable practical cir- 
cuit for ham radio* Hundreds of circuits and Ideas 
are discussed, and each one Is useful to hams. 
Here are the chapters: semiconductors, compo- 
nents and construction, receiver topics, oscillators, 
transmitter topics, audio and modulation, power 
supplies, aerials and electrical interference, trou- 
bleshooting and test equipment. Once you've di- 
gested this book thoroughly, you won't be able to 
build or modify any gear without consulting It. 

$1.50 



Technical Topics for the Radio Amateur 



by Pat Hawker G3VA 



Order from 



73 Magazine, Peterborough, N.H. 03458 



+ 




CAMEiMf 



SMILE 



You're on TV 



Ju$t think! Televising your family and relatives on 
the living room TV set with YOUR OWN TV CAMERA. 
Interested?? No matter whether you're considering a 
camera built primarily from [unkbox parts or from a 
complete kit, ATV RESEARCH has just what you need- 
Over 8 different lube and transistor models to select 
from. STARTER KITS $18.95 up . * . MAJOR COM- 
PONENTS KITS $58.25 up . . . COMPLETE KITS 
(transistorized & printed circuit) $149.50 up. 

Get started in thif FASCINAT/NG HOBBY today by 
writing for a copy of our NEW 1967 catalog. It con- 
tains a comprehensive listing of kits, lenses, vfdicon 
tubes, tripods, focus/deflection coils (both regular and 
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etc. Please include 102 to cover cost of moiling. 

fsfabf/shed dealer inquires invited. 



PABOXStt 



WW IS 





St. Sioux G*,H*. 

mm 






MARCH 1967 



109 




Over 275.000 QTH's in the U.S. edition 
Over 127,000 QTH's in the DX edition . 



. . $5.95 
. . .$3.95 



See your favorite dealer or order direct (add 25c for malt- 
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of Maps-Order Your Set Today! 









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mation on each of we ou «"" . 0Q 

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WORLD ATUS-Only Atlas compiled for 
Jmateurs. Polar proi"?™""* cont 

See jour favorite dealer or order direct. 












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RADIO AMATEUR 

ca 




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k 



INC. 

Dept. B,4844 W. Fullerton Ave. 
Chicago, III. S0639 



■V * *- HUH H 




lH*nr Paul; 

In your recent editorial you mentioned try- 
ing- to create more interest in the 2,4 GHz 
band. You may be interested in the enclosed 
photographs showing an amateeur tracking: 
experiment organized at Interstate Electronics 
by Jim Counter <K6AIP), This group success- 
fully locked on and tracked the Surveyor moon 
probe. The antenna was a surplus S foot dish 
with a home brew feed mounted on a home 
made tracking mount. The preamp was bor- 
rowed from Mel Labs. The receiver is one 
which the group in the photograph designed 
and built for NASA, It is called the "General 
Concept Receiver" and is extremely flexible. It 
covers 70 MHz to 10 GHz and is triple con- 
version. Its main application is for reception 
of narrow band telemetry and doppler from 
spare craft. Tuning is done by a "push button" 
freq u ency synthesizer. 

The success of the first experiment has re* 
suited in an organized effort to improve the 
antenna and mount for further amateur track- 
ing experiments. 

As you can see the people at Goldstone were 
quite surprised at the results of this effort- 
Sam Kelly W6JTT 
Garden Grove, California 
m, 













Kc- or kHz.? 



Caen Van N<H*k1aun 227, 
Rijswijk, Z, H. 



of admiration for 
but just this fact 
against one inac- 



Kiiitor, QST: 

Unnecessary to say, Vm as fuD 
your fine paper hs everybody else, 

urges me tin 1 stronger to protest 
runny. Some time ago yon pointed mit to all hams 
that H is much better to speak about frequencies than 
wavelengths, U iul the whole world has followed your 
example Bui when speaking about frequencies, we 
me&ti the number of cycles per second, in any case 
the nil ti i her of cycles in o certain time, and therefore 
it is wrong to spenk about frequency of, for instance, 
I4.3UU kilocycles; one should speak about kilocycles 
fer stc and, abbreviated kc/i. Nobody would speak 
about coulombs instead of amperes, but neither should 
we spealc of kilocycles when we mean kilocycles per 
second. 

New we linve a new name for this unit, the Hertz, 
abbreviated Hz, which was inter nationally adopted by 
some congress. As Hem rich Hertz was without doubt 
an eminent and leading fiim re in physics, and as it is 
easier to type and print kHz than kc/*, I think you 
hat] better adopt it, too, before you lead all hams in 
the world ustrny by the wrong 1 unit, the kilocycle, 
which you are using to-day, 

— IT. Kteman* PAOZK. 



While agreeing with the author of this letter on the 
merits of the term "kilollert/." as a unit of frequency, 
QST is inclined in this respect to follow the recom- 
mentations of the Uonuttiftee on Standardization 0/ the 
Institute of Radio Engineers, which is still at work in 
collaboration with other agencies in the standardization 
of radio definitions, nomenclature, measuring practice, 
etc. The current recommendations of thai committee 
gives the meaning **kiIocycles per second* 1 to the abbre- 
viation "k<\'\ exactly as attaches to the abbreviation 
"kHz/* The *"kiliillertie" is not yet a recognized unit 
of frequency either in this country or in the inter* 
national literature, and for that reason QST does not 

e it, — Editor 

From QST, pa*e 5K, September, 1930, 



Interested in VHF? 

Then why not send for a free sample of the 
VHF'er Magazine. If s devoted entirely to serious 
VHF and UHF hamming. It contains articles by 
well-known and capable VHF'ers. All who want 
to improve their knowledge of VHF are invited 
to subscribe. 

The VHF'er 

Parks Laboratories 
419 SW First, Beaverton, Oregon 



RTTV TT63A/FGC REPEATER 529-23 

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NEW 




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ost comprehensive how-to-build-it source 
• Problem-solver for designers & builders 

Completely revised and enlarged by William L 
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standard for electronics engineers, technicans, 
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OOP Transistor Notes 

$1FEjTs I tried the inexpensive Motorola 
FETs in a number of circuits and found 
them quite satisfactory, I would use them 
without hesitation in the second stage and 
mixer of the 2 meter converter described by 
K6HMO in the October issue, and would 
use them for all stages on six or below. 
They are about a decibel noisier at 220 MHz 
than the TI plastic-cased units (2N3819), 
but nevertheless quiter than a 4 17 A at that 
frequency, which is pretty good for a buck- 
The numbers are MPF103, MPF104 and 
MPF1G5. These are N-channel symmetrical 
FETs similar to the 2N3819, but with a 




2N38i9 MPT 105 

BOTTOM VIEW 



t9tertV 



220 or 144 MHz proamp using $1 Motorola MPFlOS'i 
or $4 Texas Instruments 2N38I9. The $4 one Is about 
a dB better. Dip the coils to frequency. The input 
tap is about 50% up, output is 20%. Adjust every* 
thing lor best NF. WIOOP got 1.8 dB, 



different base. The MPF105 has the highest 
transconductance and the lowest noise fig- 
ure. Its best NF is at zero bias, also like 
the 2N3819, MPF is about a buck; the 3819 
is about four. The MPF 105 is equal in noise 
figure to a 6CW4. I got 4.1-db NF at 220 
MHz with the best of the Motorola units 
and 2.5 dB for the best 2N3819. 

Fairchild 2.V4122: I am really impressed by 
the Fairchild 2N4122, It isnt more anything 
than anything, but it is silicon, and it is a 
good replacement for PADT and such ger- 
manium transistors where heat turns out a 
problem. (Note that silicons may not be very 
good below zero degrees F, though the ger- 
manium transistors get better down as low 
as you are likely to get.) The 220-MHz NF 
of 4-5 dB of those I measured beats the 
Philco T2028 and is about even with the 
2N2398 and 2N2494-5, considered very good 
three years ago, Price under a buck. Also 
good for audio. 

GE16K2: GE's 16K2 is a good NPN silicon, 
cheap, for local oscillator chains and such, 
NF is 3.5 to 4.8 dB at 220 MHz for 20 units. 
It's similar to the Fairchild 2N3563. 

TI XM101 vs TI XA/10: We've run some 
interesting comparisons of the TI XM101 
(about $20) and the TI XM10 (about 94c). 
220-MHz NF of the 101*8 was 1.9 dB. One 
lot of XMiO's ran 2.0 to 2,5 dB. The late, 
lamented, XM05-6*s ran about 30% under 2 
dB, with 1.5 and L75 measured, 



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ASBURY PARK, NEW JERSEY 07712, U.SA, 




112 



73 MAGAZINE 



150 MHz converter: Last week I made a 
150 MHz converter for lab use. With four 
under $1 types, I had a 3-dB NF. For any- 
thing better, another rf amplifier would be 
needed. 

Fairchild 2N4342: I tried out the Fairehild 
P-channel 2N4342 FET. NF 6 to 7 dB at 
220 MHz > which, with a 5 dB second stage, 
is about even with a short, Don't know if it 
had any gain or not, I had five, tried only 
three. 

The above notes are all from Hank Cross 
WlOOPj who is generally accepted as know- 
ing what he's talking about. The information 
on prices is approximate and subject to 
change or error. Get the specifics from 
vour distributor. 



Kindly Keyer 

Dear Paul, 

I have had considerable correspondence 
considering "The Kindly Keyer** in the July 
73", It appears that there were a couple of 
minor problems in the article as it appeared, 
which we failed to catch. 

First, there are a few discrepancies be- 
tween the schematic and the px, board 
layout: 

Corrections to p.c. layout, page 49 

1. Qs and Q n (labels on same) should be 
interchanged, 

2. A 33K resistor should be shown be- 
tween base of Q 5 and emitter of Q 6 . 

These are the only real errors which 
should be straightened out. However, in the 
case of Q 1 : 

3. The 100 k could be changed to a 220 k. 

4. The .l^F capacitor could be a *22 F. 

4, The .1 F capacitor could be a .22a*F. 
(These only affect the time constant of 
the blocking oscillator, and any combina- 
tion would work, with a different setting 
of the speed pot.). 

5, The 82ft resistor could be attached to 
+4.5 V. (This makes the side tone louden) 
Notice that the order of components in 

the base of Q, is different, but since they 
are in series, there is no electrical differ- 
ence. Even a novice should know this, but 
it seems to bother some! 

6, Labels could be affixed to three ter- 
minals in Qt - Q.j block as shown. 

These changes would result in perfect 
agreement of p.c. board and schematic, but 
only 1 and 2 seem worthy of mention- 

George Daughters WB6AIG 



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No coils or traps to distort the radiation pat- 
tern. The design results in increased capaci- 
tance* and therefore, shorter length, for reso- 
nance, (deal for places where a full-length 
dipole is too long. 

The 160 m Barb'd wire antenna is only 186 
feet long. The 80/75 Barb'd wire antenna is 
only 94 feet long. The 40 m Barb*d wire an- 
tenna is only 48 feet long. The 20 m Barb'd 
wire dipole and beam is only 24 feet long. 

Feed with 50/75 ohm coax — no mafchinq 
devices required. 

Send a $2 U.S, money order for mailing and 
handling of pictures and instruction sheet for 
building your own, 

C. LeRoy Kerr, WA6CTK 
P.O. Box 444 

Montebello, California 90641 



IW2NSO from page 2) 

stitule hud plenty to do on its hands just 
filling in those areas where the League 
should have been active, but wasn't. Pos- 
sibly this was a mistake. I suspect now that 
many more amateurs might have joined the 
Institute if it had been formed as a direct 
opponent of the ARRL, complete with hun- 
dreds of appointed officials all over the 
country to spread the gospel from head* 
quarters to the grass roots members, hoked- 
u p elections of cardboard directors with no 
real say or even awareness of the real forces 
running tilings, official bulletins, inconse- 
quential "services" and the whole ball of 
wax. 

No, I goofed it- We set up with minimum 
of overhead, sent inexpensive letters to Con- 
gress, and ran the Institute without all the 
hoopla and big salaries. We also ran it 
without very mam members for I found, 
to my intense disappointment, that without 
the Big Show there were very few dollars 
• * . or members to speak of, I tried telling 
the straight facts in my editorials, but found 
myself being called interesting names for 
trying to ruin the ARRL, Oh, I've centainly 
been critical of a couple of the top men run- 
ning the League, no question of it. Few 
people have noted that none of these gentle- 
men will face me in public and answer my 
criticisms, But IVe intentionally kept the 
Institute completely out of any hassel with 
the League and kept it on its published aim 
of speaking up for amateur radio in Wash- 
ington. 

All current members will receive a long 
and detailed account of the history and 
philosophy of the Institute, as well as a 
complete and detailed account of the income 
and expenses. And there'll be none of this 
Lgue coverup yon find in the ARRL annual 
report. 

How great is the disaster? In August 1966 
there were six new members . . . September 
five , . . etc. There is no question at all that 
very few amateurs believe that there is any 
importance in th goals of the Institute. I 
suspect that the best plan is to not make any 
further effort to promote membership. I'll 
do what I can at my own expense to send in- 
formation about amateur radio to Congress. 
Barry Goldwater has made some excellent 
suggestions for getting the most out of the 
least effort along this line. Tin going to keep 
pitching , . . sorry T tailed to interest very 
manv of you in the idea. 



I 14 



73 MAGAZINE 



M :ca Cottdsr .006 ® 2500V , • . . -4/S1 

Snooperscope Tub* 2" $5, .. .....2/S9 

Minni-Fan 6 or l2Vae/G0 Cys $2® 3Y$5 

4X150 Ctramre Loktal SJ.25^ 4/2 

Line Filter 20OAmp 130V AC 55® ,. .5 $20 
DC 3'V Meter RD SOOMa S4^....2/S7 
PC 2* 2 " Meter 'RD 30V DC $S#....2/$5 
DC 4" Meter RDihfa/$5@ 2/S9 

Szcket Ceramic 1625 Tube 4/JI , 10/12 

Socket Granite 4X150 Loktal ..4/S2 

Wanted 304TL - Top $$ Paid ! t 
2 5M H PiHouod 500Ma Choke, .3 for $l 
Krwb Sp:it-Cra;k BC34S S» (ft* . .3 for.S2 
MiTiiFan 6 or (2 VAC $ 1 .50^},. .4 for $5 
Beam Indicator Selsyns 24VAC 2 for SlO 
Precision TLI47 Feeler Relay Gn^e ..SI 

Fuse 25GMa 3AG 50 for $1. 300/12 

XMTTG Mica Cotldsr .006{S) 2.5Kv..2/$l 
W,E, Ptlnr Relay ^255A/$5^ .. ,2 for $9 

W,E. Socket for #255A Relay $2.50 

Toroirfs mtilhy Now Pckn $<0 6/S5 

&.3VCT @ J5.rA & 6.3VCT @ 2A $5 @), 
200 KC Freu Std Xtals $2®..\2/», 5/$5 
Print il Ckt Bd Now Blank !Jx|2" Si® 

Klixon SA Reset Ckt Breaker $l@_IQ/$5 
Lino Filter 4.5A@ I I5VAC. ».. .*5 for $1 

Line Filter 5A (&I25VAC . . ,3 for SI 

8 GA Xfmr 2.5V/IQA/ IQKv/lnsI $2 

Cnok» 4HY 0,5A 27Q$3@*...>....4/*lO 

Sevens Precision Choppers $2(?3) 3/S5 

HtJm ts Multi Ten-Turn®, .• . SI 

H eh pat Dials $4@ 3/$IO 



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PL259A & $0239 CO- AX M&F Prs, 
Phone Patch Xfmrs Asstd 



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3A & 
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forS2 
for 55 
SI 
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.3/$ I 



Insttd Binding Posts .20/51 

Sun- Cells Selenium Asstd 6/ SI 

.01 Mica 600WV Conds 6/$1 

.001 to .006 Mica/l200WV Cifsr. . - * .4/$l 



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PtfP 30 Watt 3A, 2NII5. 156. 235, 242 
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PNP 2N670 3C0MW 35e^ w ......5 for SI 

2N;C39 2N6FI^I Amp........ 4/Sl 

PNP 25WTO 2N53B. 539, 540. . ^2 for SI 
PWR Finned Heat Sink ISO SQ". .$1.50 

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SILICON PNP T05 Sl TOI8 PCKG 

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DX Flash 

The DXers may be interested to know 
that as far as WTW credits for countries are 
concerned that not only do we accept any- 
thing as a country that is accepted by any 
national amateur radio society, but we feel 
that if a fellow operates from a country then 
contacts with him should count for that 
country. We do not feel that we should try 
to set ourselves up as official arbiters on 
exactly how legitimate a license is for any 

spot. 

In the U.S. there is little question about 
licenses. Either you have one or you don't. 
But once you get off the beaten path it is 
difficult to set up firm rules. In Nepal there 
is, the last I heard, one and one only legiti- 
mate licensed amateur and that is Father 
Moran 9N1MM. But other amateurs can 
and do operate with the knowledge and 
unofficial consent of the government. This 
same situation is true in several other coun- 
tries I have visited , , , and tilings are even 
looser elsewhere, It becomes almost capri- 
cious to try to set oneself up as the "official" 
decider as to what is or is not licensed. 
Hence our decision that if he is there it 
counts. 



WE WANT TO BUY 

Surplus Aircraft Radio & Test Equipment 

We will pay cash or trade you (whatever you need) 

for the following items: 

Test Equip!, Signal Generators, 

Measurements Corp. Models 65-B 

Boonton Radio Co, Models 232A, 235A. 

Hewlett-Packard Co. Models 608D, 6I2A. 624C. 

Military Models. SG-IA, SG-2, SG-il, SG-66A, MD-83A K 

TS-5I0A. 
Aircraft Navigation & Communication Equipt. 
ARC-34, AfcC-38. ARC-52, ARC-73. ARN-14, ARN S9, 

ARM -73. 
Aircraft Instruments. 

ID-249A, ID-2S0A f ID-251A, ID -351 A,, 10-387. 
We also want late type Aircraft Radio and Radar equip- 
ment manufactured ty Collins Radio Sendix Radio and 
Aircraft Radio Corp, 

Write, Wire or Phone if you can supply any of these. 
Ask for Norm Eichner. 

Norman Electronic Sales 

1413 Howard St. Chicago, III 60&26 




73 Magazine 
CUMULATIVE INDEX 

October 1960-December 19o6 

Now available for 25c 

73 Magazine 

Peterborough, N.H. 03458 



MARCH 1967 



115 






Technical Aid Group 

The first members of 73's Technical 
Group are listed below. They are 
willing to help other hams with their 
technical problems. If you have a con- 
cise question that you think can be 
answered through the mail, why not 
write to one of the hams on the list? 
Please type or write legibly, and include 
a self-addressed stamped envelope. One 
question to a letter, please. 

If you'd like to join the Technical Aid 
Group and you feel that you are quali- 
fied to help other hams, please write 
us and we'll furnish complete informa- 
tion. It's obvious that we need many 
helpers in all parts of the country and 
in all specialties to do the most good. 
While 73 will try to help with publicity 
and in other ways, we want the TAG to 
be a ham-to-ham group helping anyone 
who oe*ds help, whether they be 73 
readers or not. 

Don Nelson WB2EGZ, EE, 9 Green- 
ridge Road, Ashland, NJ. 08034, VHF 
antennas and converters, semiconduc- 
tors, selection and application of tubes. 

Tom OHara W60RG, 10253 East 
Nadine, Temple City, Cal. 91780. ATV, 
VHF converters, semiconductors, gen- 
eral questions. 

Stix Borok WB2PFY, high school stu- 



dent, 209-25 18 Ave,, Bayside, NT. 
11360. Novice help. 

George Daughters WB6AIG, BS and 
MS, 1613 Notre Dame Drive, Mountain 
View, Calif. Semicondiictors, VHF con- 
verters, test equipment, general 

Roger Taylor K9ALD, BSEE 2811 W. 
William, Champaign, 111. 61820. Anten- 
nas, semiconductors, general, 

Jim Ashe W2DXH, R.D, 1, Freeville, 
N,Y. Test equipment, general 

J. Bradley K6HPR/4, BSEE, 3011 
Fairmont St., Falls Church, Va. 2204& 
General. 

Howard Krawetz WA6WUI, BS, 654 
Barnsley Way, Sunnyvale, Cal. 94087, 
HF antennas, AM 3 general 

Robert Scott, 3147 E. Road, Grand 
Jet, Colorado 81501. Basic electronics, 
measurements. 

J. ], Marold WB2TZK, OI Div USS 
Mansfield DD728, FFO San Francisco, 
Calif. 96601. General. 

Hugh Wells W6WTU, BA, 1411 18th 
SL : Manhattan Beach, Calif, 90266, AM, 
receivers, mobile, test equipment, sur- 
plus, repeaters. 

Richard Tashner, WB2TCC, 163-34 
21 Road, Whitestone, N. Y. 11357, High 
school student, general. 

Wayne Malone W8JRC/4, BSEE, 
3120 Alice St., West Melbourne, Fla. 
32901. General 



{Continued from p&gs 4) 

to pay for equipment to the movement to 
form an effective Canadian amateur organi- 
zation instead of expecting Canadians hams 
to be a small division of the US ARRL. In- 
cidentally, it sounds like this is an excellent 
year to visit Canada. From all indications, 
Expo 67 will be a far more satisfactory 
world's fair than the one in New York, May- 
be well see you there. 

So there are the special issues of 73 com- 
ing up in the next few months. Each issue 
will also feature the usual selection of what 
we hope will be interesting, informative and 
entertaining articles. Be sure to be with us. 



Writing for 73 

So many people have sent for copies of 
our booklet, "Writing for 73/' that weVe had 
to reprint it. If youve thought at all about 



writing for publication, why not send us a 
self-addressed business envelope and well 
mail one out immediately* I have also com- 
piled a list of articles Fd like to have for 73. 
Please mention if you'd like the list, 

TAG 

The Technical Aid Group (TAG) is 
starting to help hams with their technical 
problems. However, we need many xn©re 
helpers to be able to work effectively* If 
you feel that you're competent to help, and 
have a few extra hours to devote to helping 
other hams, we'd like to hear from you. Your 
main reward from this work will be a sense 
of satisfaction and a little publicity, though 
there are a few other benefits. Please write 
for details, 

. . . Paul 



116 



73 MAGAZINE 



Propagation Chart 



MARCH 1967 



J. H. Nelson 



EASTERN UNITED STATES TO: 



QM i 



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11, 



# Very difficult circuit thii hour. 

* Next higher frequency may be useful fhii hour. 

Good: 1-5. 7-17. 19-22. 26-31 

Fair: 23. 25 

Poor: 6, 18, 24 

VHF DX likely: 6. 13, 14 




6 METER SOLID STATE 
RF CONVERTERS 

2 db NF. ,2 fiv for 6 db signal to noise ratio, mil. 
spec, epoxy glass printed circuit board, variable for- 
ward gain control, built-in power supply available 
for all models, 2N3S23 FET front end available for 
1.5 db NF and reduced cross-mod illation effects. 



THESE CO 

Model 

SS610 

SS610F 

SS611 

SS611F 

SS610 

SS511 

SS600X 

SSG60XF 



NVERTERS CAN REALLY PULL IN THE DX1 

Input M Hz Output M Hz Price 

50-54 14-18 $21.95 

Same as above but FET rf amp. 39.95 

50-54 7-11 21.18 

Same as above but FET rf amp. 39.05 

50-54 MHz rf pre-ampliner 9.H 

60-54 MHz FET rf pre-amplifler 29.95 

Special IF (.6-30 MHz) 24.95 

FET special IF (.6-80 MHz) 42.95 

For built-in power supply, add 5.00 



For prompt shipment of stock models include postal 
money order or cashier's check. Special models 
shipped within six weeks, Personal checks must 
clear before shipment. Include 20% deposit for COD* 

Unconditionally guaranteed. 

Southwest Semiconductor Specialists 

P.O. BOX 12312, SAN ANTONIO. TEXAS 18212 



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oscillator/monitor 

• a term five broadband RF detector 
give* audible tone signal in the 
presence of any RF field from 10 mw 
to! kw and lOOkc to lOOOmc 

• a CW monitor with positive "RF" 
switch uses only 6** pickup antenna 
and NO connection to rig or key 

• a code practice oscillator with 
adjustable lone & built in speaker 

• high gain 4 transit tor c ire if it 
powered by long life AApencefl 

• 16 gouge aluminum cabinet in 
white & black eoojty finish, 3 1/j " 
by 2 Vi" by 1 '/4 " r weight 8 ounces 

• 100% US mode and guaranteed 

the James research company 
11 schermerhorn sf v brooklyn n.y. 11201 




1 095fb«ttintl) 
I J-m ppd use & ton 
send cert ck or m.o, 
ny res add 5% tax 



I 

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Turn your hobby into 
steady high-pay job 



WORLD'S HAPPIEST MEN love their jobs. 
Wouldn't you love a career in radar or AM, FM, 
TV, or microwave broadcasting? Or in servicing 2- 
way systems as your own boss? Learn at home. Nine 
out of 10 who complete our personalized home study 
course pass the Commercial FCC exam on their first 
try. {You will too, or your tuition is refunded.) 
Without our training, 2 out of 3 men fail* 

FOR FREE BOOKLET, "How to Get a Commercial 
FCC License/' plus our school catalog, send name 
and address to Cleveland Institute of Electronics, 
1776 E. I7th St., Dept ST-10, Cleveland, O. 44114. 






GENERAL SURPLUS SALES 

"LET ONE DOLLAR DO THE WORK OF TEN'* 

0-1 MA METERS— Extra large, 2%"H x 2%"W 
full clear plastic face, calibrated in four easy 
to read ranges, 0-9 s units, 20-60 db. 0-100, 0-3 
watts. 0-H watts. Mounting bracket included — 
S3 .95— BRAND NEW. 

POWER TRANSFORMER— 117 vac, 60 cy pri- 
mary, 30 vet @ 1.0 amps secondary. Excellent 

for transistor power supply $2,30 — BRAND 
NEW. 

ROTARY SWITCH, spring return, Oak Mfg. 
Co, 2 sections, 3 positions 7 poles, 3 throws* 22 
fixed contacts, 7 moving contacts. Ceramic in- 
sulation U'altXlliWxl-S/lfiH. Made for trans- 
mit switch— BRAND NEW 98c. 

TERMINAL KIT, neat convenient terminal 
boxes. Makes a professional wiring job of any 
installation. Conceals unsightly wiring, pre- 
vents accidental shorting. Removable terminal 
strips. Special adhesive backing allows mount- 
ing directly to desks, panels, etc. Available in 
three sizes; 2 sta x 4 lugs $1.49 4 6 sta x 4 lugs 
$2.95, and 6 sta X 8 lugs $4,95 BRAND NEW. 

Knobs all aluminum fits J4* half flat shafts, 5 
for $1.00. 

Resistors, capacitors, switches, pots, coils — no 
oddballs another General Surplus buy at 
$1.00 per pound 

Terminal Boards, excellent for experimenters, 
loaded with resistors, diodes, capacitors excel- 
lent values 2 for 98c 

TERMS — no C.O,D. all prices FOB Bingham- 
ton, N.Y. Add 25c for postage and delivery* 

GENERAL SURPLUS SALES 

10 Alice St., Binqhamton, N. Y. 



WE TRY HARDER TOO. OUR PLAN 1$ MORE 
EQUIPMENT FOR LESS . . . READ ON , . 

Frequency Meter covers from I2u kc to 2G mc and up, ex- 
cellent construction. Internal filyslal, ttraighLforward design, 
lyjw IM (Uke BC221K i $34,50 

Scape, Mull I -Beam, 1P37/APA-74, perfect for building proj- 
ects, very neat cite with few holes, size and ah ape of stand- 

Scope well known Tektnmii 514D. with deUy line* iraooth 
oprmtan, professional quality » . * . . $225*00 

Scope, equivalent to above, but costs leas, Dumant typo 330 A 
ui- iji j lino ioo i . ti.t i («i * t t «*»■-**•*■ .*■•«. * ,*«■>#, J l jy.uil 

Transmitter, FM. biz band, vhf, FHTItU ....$49,98 

Transmitter, 400 watts. TV 435 mc, rare and haid to find 
ART 28. push pull 4X150$, bargain ...**.... $79,50 

ART- 1 3 & commercial power supply, 115 vac.... ,,$95,00 

Fun, play cops an oederi or other fun games with APN-1 
dopplet style radar, excellent ..... $9.48 

Send stamped addressed envelope for list 

THE R & C WILSON COMPANY 

Box 393, Littleton, Colo. 80120 



bARBER TRAVEL ... we Hke to think of 
ourselves as the ham's travel agency. For 
Ham-Hops, personal tours, or DX-peditions 
or make it a fly-drive tour (we loved it). 
You pay no more for expert assistance. 
and you don't have the headaches, 
BARBER TRAVEL-Ruth Barber K1IIF- 
Jack Barber W1PRT. 711 Cottage Grove Rd.. 
Bloomfield, Conn. 06002 (203) 242-2279. 



TTU3A REPEATER- REGENERATIVE. Helps receive 
biassed-distorted signals, sUbo eerves as a RTTY converter. 
Complete with tubes, wetted relay, cable and instructions 

on putting this unit Into service. Like new . .$25.00 aa, 

RTTY DUAL FREQUENCY SHIFT TONE CONVERTER. 
Northern Radio up© J 5-, each tone converter la self con- 
tained Including power supply, complete with tubes, con- 
version details and schematic. Used, good. $32.00 ea. 
Sand us your teletype requirements. 

ATLANTIC SURPLUS SALES 

250 Columbia St., Brooklyn. N,Y. 



New Products and Books 




Eico 711 



Exo's newest communications product is 
their 711 Space Ranger Short Wave Com- 
munications Receiver. It covers ,55 to 30 
MHz with a RFC), handspread, S-metcr. Its 
cabinet is attractive enough for the living 
room. In kit form, the 711 is 849*95; wired, 
it's $69.95. You can get more information 
I'ram Eico, 131-01 39th Ave,, Flushing, N, Y. 

Denson Catalog 

A surplus catalog to really make you 
drool is the new* 160-page catalog from 
Denson Electronics Corporation. Al Denson 
W1BYX has spent a tremendous amount of 
time photographing, listing and organizing 
his stock and the results are very impres- 
sive, Al specializes in television equipment, 
but the catalog contains surplus and used 
equipment of every description. Of special 
interest to the TV ham is a complete bibli- 
ography of articles on ham TV and many 
reprints of articles on TV in the catalog. 
The catalog costs 50c; it's worth far more 
than that for the reference data alone. Den- 
son Electronics, P. CK Box 85, Rockville. 

Oscilloscope Measuring Techniques 

The s e r i o us electronics experimenter 
knows that an oscilloscope is the most val- 
uable piece of equipment available for test- 
ing. However, few hams take full advantage 
of their scopes. An excellent book about 
scopes and their uses is Oscilloscope Mea- 
suring Teehnioques by J. Czech. The book is 
the English edition of a book published In 
German by Philips, and it is very complete. 
The first 250 pages of the book are devoted 
to scope circuits and construction, the next 
120 pages to general measuring techniques, 
the next 170 to specific techniques and the 
last 50 pages to scope photography and pro- 
jection. The book costs $15,80 and is avail- 
able from Springer-Verlag, 175 Fifth Ave., 
New York, N.Y. 100 IO- 



NS 



73 MAGAZINE 



Low Cost VHF Antennas 



A new line of low cost VHF "Space-Saver" 
antennas for 120-480 is being manufactured 
by International Crystal Mfg. Co. The an- 
tennas feature full performance, solid 
molded bases, case of installation. Mobile 
and fixed base units include a vertical mo- 
bile for $5.25, vertical ground plane with 
universal mount $8.50 or with pipe mount 
$10.95. dipole with pipe mount S 11.95, and 
the attic or base antenna with universal 
mount for $6.95. Special coax cable kits for 
use with antennas are priced at S3. 95 and 
$4,95, For complete information write Inter- 
national Crystal Mfg. Co., Inc., 18 North 
Lee, Oklahoma City, Oklahoma 73102. 

RCA Receiving Tube Manual 

The new edition of the RCA Receiving 
Tube Manual (RC-25) contains over 600 
pages of information on electron tubes and 
their uses. The first 100 pages contains a 
wealth of data on general characteristics of 
tubes and how they should be used. The next 
400 pages lists all receiving tubes made by 
RCA— virtually all receiving tubes— with all 
of their characteristics. The last section of 
the book contains many applications of 
tubes, with specific circuits and description 
of how they work. The book is a tremendous 
buy at $1.25. Buy at your dealer, or order 
from RCA Commercial Engineering, Harri- 
son, N. J. 07029. 




Hammarlund Hp-205 

The new Hammarlund HQ-205 is a gen- 
eral coverage receiver with a built-in 5 watt 
10 meter or CB transmitter. Electrical band* 
spread is on 80-10 meters as well as CB. The 
receiver tunes .540-30 MHz. It includes a 
variable BFO, Q multiplier, XL and S meter. 
Price is S259.00. You can get more infor- 
mation from Hammarlund Amateur Prod- 
ucts, 73-88 Hammarlund Drive. Mars Hilb 
\. C, 28754. 




COMPRESSION AMPLIFIER $29.95 

These government surplus limiting amplifiers of- 
fered at a fraction of their cost and they are brand 
new unused. Input & output impedance of 600 
Ohms, self contained 115 volt 60 cycle power sup- 
ply. Gain 36 db plus or minus 1 db. Upgrade your 
shack for professional performance with this beau- 
tiful rack panel commercial grade equipment. DB 
out meter on front panel. 



40 AMP SILICON DIODES 



50 
100 

200 
300 
400 
500 



PiV 



$ .80 




600 


1.00 




700 


1.50 




800 


1.75 




900 


2,00 




1000 


2.40 







$2,75 

3.00 
3.40 
3.80 

4.20 



INTEGRATED CIRCUITS 

T085 flat packs with specs. 

Computor quality 3M magnetic tape. 

New boxed. 1" x 1800', 

240 Amp 100 PIV silicon diodes. 



2/$l,25 

$7.50 

$4,00 



29 VOLT 50 AMP DC REGULATED 

Operate on 115 volt 60 cycle input with output of 
29 volts DC 50 amps filtered and regulated. Solid 
state components with standard 19 inch rack 
panel mounting, Excellent condition. Shipping 
wgt. 175 lbs, $75.00 

29 VOLTS DC 35 AMPS REGULATED 

Same type power supply as above with lesser out- 
put Of 35 amps. $65,00 

1600 VOLTS DC 1.8 AMPS REGULATED 

Solid state circuitry, 115 volt 60 cycle input, rack 
panel mounting* filtered with 0,5% ripple. Only a 
few of these on hand. Shipping wgt. 175 lbs. $75.00 



1.5 AMP MIDGET SILICON DIODES 

1000 PIV 50* each 12 for $5.00 
1400 PIV 65^ each 12 for $6.50 



GEIGER COUNTER CHASSIS assembly, fully wired, 
transistor power supply operated from 9 volts, 
with 100 microamp meter. Less geiger tube. With 
schematic. $4*00 each 

LIGHT ACTIVATED SCR CLASCR) 

Function of an SCR triggered by light thru the 
glass window top of the TO-18 unit. Various ap- 
plications in tape readers, character recognition, 
logic circuitry, relay replacement, night lighter 
brain. Offered at a fraction of list price . . , only 
smalt quantity available. 



25 


PIV 


$ ,75 




200 


$2.30 


50 




1. 00 




300 


2.70 


75 




1 35 




400 


3,20 


100 




1 .60 




500 


4.00 


150 




2.00 




Under 25 V 


,50 



New Fall catalog hot-off-the-press. We keep no 
mailing lists. Send 25* for the best 80 page cat- 
alog we have ever printed. More bargains than 
ever before. Ml material FOB Lynn, 





SHNA 



19 ALLERTON ST.. LYNN, MASS. 01904 



MARCH 1967 



119 



A.R.C. SALES 

Filament and Bias Transformer, 115V. 60 eye. 
pri. Sec. 1, 12.6v.CT, (§ 7.5 A, Sec. 2, 185v, & 50 
ma. Wt 1 Jb. $4m 

Filament Transformer, 115v, 60 eye. ori. Sec. 1. 
6,3v. @ 6A. Hook Sec. 1 and 2 together Sec. 2. 
6.3 @ 5A. for 12.6v use, Sec* 3, 6.3v @ 6A. Wt. 
5 lb. $3-50. 

Plate Transformer. 120v. 60 eye. prl Sec.SSOv, 
C.T. @ 200 ma. Wt 8 lb. $2.50, 
Hammarlund Dual section variable condenser. 
20-450 mmf, per section. .125 spacing. 4 3 / 8 "w x 
2V 2 "ti x 11" long plus 1" for »V shaft. Wt 3 lb. 
$4.50. 

Cardwell variable condenser* 25-500 mmf, .125 
spacing, 4 l V'w x 2 1 / 2 "h x 7" long plus 1" for 
shaft. Wt. 3 lb. $3.75. 

All items are new 
and F.O.B. Worth ingt on, Ohio. 

A.R.C. Sales, P.O. Box 12, 
Worthingion, Ohio 43085 






INVERTERS 



tfV DC 

u* liiie I2v equipment 
6 v systems 



on 



TO 12V DC 

66 WATTS $43.50 
130 WATTS $69.50 
250 WATTS $ 73,50 



We oko moke 12vdcto I2vdc 12vdc to 2 8vdc 
12vdc to 115y 60cps 150 or 300 watt 

12vdc to 115v 400cps ISO or 300 watt 

12vdc to 450vdc 

WRITE for complete information 



INVERTRONICS 



P.O. BOX 342 
PINE BROOK, N.J, 



VHF-UHF 



Converters and Preamps for 50 thru 432 Me. 

Write for literature, 
Send for a sample copy of the VHF'er, the 
only magazine for VHF and UHF hams. 

Parks Electronics, 419 S.W. First Beaverton, Ore. 



CQ de W2KUW 

5% BONUS!! 

Pqid over any top offer for any piece of aircraft or 
ground radio units, also test equipment. All types of 
tubes. Particularly looking for 4-2EQ • 4-400 • 833A 

• 304TL • 4-T000A • 4CX5000A et ol. 17L • SIX 

• 390A ■ ARM • GRM • GRC • UPM • URM * USM 
units. 

TED DAMES CO. • 310 Hickory St., Arlington, N.J. 



*TW0-WAY* 

COMMUNICATION CRYSTALS 

AMERICAN CRYSTAL CO. 
PO BOX 2366 KANSAS CITY, MO. 



PLATE TRANSFORMERS— 539 95 

36004-3600 VAC @ 1000 Ma. t CCS, with 120/240 VAC 60 
cps primary- Commercial quality units manufactured 
by Wagner Electric Co. measure 13" high 12" wide 
and 9 M deep. Net weight is 85#. Price $39.95 F.O.B. 
Minneapolis. One year unconditional money back guar- 
antee, Terms: Check or M.O. with order. Immediate 
delivery. Write or phone; 

PETER W. DAHL CO. 

3314 Diamond Drive El Paso* Texas 



Designs & Construction of 
Electronic Equipment 

In this new book by George Shiers* the 
author acquaints beginners with the proc- 
esses and problems of designing and build- 
ing electronic equipment while at the same 
time providing experienced technicians and 
designers with much practical assistance. 
This text covers chassis design and layout, 
panel layout, component boards, wires and 
cables, connection methods, printed cir- 
cuits, fasteners and finishes- It also pro- 
vides a great deal of practical information 
on circuit protection, interference, shield- 
ing and grounding and environmental prob- 
lems such as heating, cooling techniques 
and corrosion. This book is filled with ex- 
cellent illustrations and drawings; a num- 
ber of useful tables are also included for 
the prospective electronic designer. For the 
amateur who builds his own equipment, this 
book provides a wealth of very useful and 
practical information, SI 4.00 from your 
local bookstore or write to Prentice-Hall, 
Inc.* Englewood Cliffs, New Jersey 07632. 

G and G Catalog 

A new 24-page Catalog of Communica- 
tions Electronic Equipment has been pub- 
lished bv G & G Radio Suoply Gompam 
75-77 Leonard St. New York, N. Y. 10013. 
The catalog, which is fully isllustrated and 
contains complete technical information, 
covers military surplus receivers, transmit- 
ters, power supplies, test sets and associated 
equipment, including dynamo tors, tranmit- 
ting crystals, special purpose tubes and head- 
sets. Copies are available from G & G Radio 
Supply Company for 25c refundable with 
first order. 

Amperex Components Catalog 

Amperex makes some very nice electron- 
ics components that aren't well known to 
most readers of 73 because they aren't 
handled by any of the distributors we usual- 
ly buy from. However, they've put out a 
catalog that should be of interest to all de- 
signers and buyers for manufacturing com- 
panies. The catalog contains condensed list- 
ings of electrolytic, foil, ceramic and vari- 
able capacitors, linear and non-linear resis- 
tors, speakers and knobs. Copies may be 
obtained by writing on company letterhead 
to Amperex Component Division, Hicksville 
N.Y. 11802, 






Directory of Electronic Circuits 

In his new book Matthew Matxll presents 
a unique and valuable took for amateurs, 
technicians and engineers; a very compre- 
hensive directory of more than 150 circuits 
used in all fields of electronics. Each of 
these circuits is completely analyzed in a 
very readable manner, and typical circuit 
values are provided along with the equations 
and formulas that describe their operation. 
To provide a more useful tool, the author 
has grouped the circuits into general cate- 
gories and provided a detailed cross-refer- 
ence system throughout the book, While 
the emphasis has been placed on transis- 
torized circuits, vacuum tube circuits are 
detailed for comparison purposes or where 
they find a special application. Some of the 
categories of circuits are amplifiers, modu- 
lation and demodulation circuitry, filters, 
attenuators and pads, oscillators, power con- 
trol and supplies and pulse circuits. In addi- 
tion, a handy glossary of the most frequent- 
ly encountered technical words is provided 
along with an appendix containing unit 
values, conversion factors, color codes and 
other useful electronic information. In all, 
this book is a very useful text that should 
be of interest to old timer and novice alike. 
$10,00 from your bookstore or write to 
Prentice-Hall, Inc., Englewood Cliffs, New 
Jersey 07632. 

FET Projects 

The latest book in Motorola's line of HEP 
publications in Field Effect Transistor Pro- 
jects. It is a step-by-step instruction manual 
on projects that can be made with Motorola 
HEP FETs and other components. The pro- 
jects are a vibrato for electronic musical 
instruments, an audio mixer, a timer, a crys- 
tal oscillator (such as a 100 kHz calibrator), 
and hi-fi preamplifier, and a dc voltmeter. 
The book also includes a short section on 
FET theory and const ruction practices. Com- 
plete building instructions are given for 
each project, including layouts, 

Quaker Electronics Tech Manuals 

Quaker Electronics has published a cata- 
log of technical manuals they have for sale. 
The catalog also lists a number of very com- 
mon pieces of surplus for which they have 
schematics. You can get the catalog for 25c 
from Quaker Electronics, P. O. Box 215, 
Hunlock Creek, Pennsylvania, 




2? 3? 4? 5? 6? 
FORGET 'EM ALL! 



The woods era full of competitor! 
who try to fell you how many mil- 
lions they have, how big-hearted 
they are, how much they'll pay 
you for your equipment— and blah, 
blah, blah. FORGET IT* FORGET 
'EM ALLI You can afford to forget No. 2, 3, 4 S 5, 6 — 
when you do business with Number Onel Whaf others 
promise — COLUMBIA delivers! We want to buy elec- 
tronics and test equipment — both military and com- 
mercial. If you have a single piece or a trainload — 
we'll pay you the top dollar for that equipment — 
bar none! We airmail your check the same day your 

foods arrive. On top of that — we pay the freight! 
ave time, money, headaches and aggravation! Tell 
us what you have — what you want! And P.S.: Do it 
todayE 

COLUMBIA ELECTRONICS, Dept. 7 

4365 West Pico Blvd., Los Angeles, Calif. 90019 

Phone: (213) 938-3731 



ALL BAND TRAP ANTENNA ! 




Reduces Interference and 
Noise on All Makes Stiort 
Wave Receivers. Makes World 
Wide Reception Stronger. 
Clearer fin All Band's! 





For ALL Amateir Transmit- 
ten. Rated at 1000 Witts 
AM 2000 SSB PiNet nr 
Llnfc Direct Feed. Light, 
Neat, Weatherpraof* 



Complete nfl shown total length 102 ft. with 9G ft of 72 ohm 
balanced tw inline. Hi-Impact molded resonant traps, (Wt. ;■) 
oz. 1" x fr" longL Yo« just tune to desired band for beamlifct 
results. Excellent for ALL world-vide short-wave receivers And 
amiteur transmitters. For N0VIPE AND ALL CLASS AMA- 
TEURS! NO EXTRA TtWKRS OR GADGETS NEEHKD! Elim- 
inates 5 separate antennas with excellent performance proren. 
Ineonspkiotis for Fnssy Neighborhoods! Xo HAY-WHIG HOUSE 
APPEARANCE 1 EASY INSTALLATION! Thousand* of users. 

75-40-20-15-10 meter bands. Complete .,.,.., $19. 95 

40-20-15- 1U meter. 5 4 ft. (best for awl's). Complete , $18.95 

SEND ONLY $3.00 (cash, ck. f mo) mid pay postman balance 
COD plus postage on arrival or send full price for postpaid de- 
livery* Complete installation & technical instructions furnished. 

MIDWAY ANTENNA • Dept. A7-1 • Kearney, Nebraska 



SURPLUS NEEDED 

Guaranteed highest prices. Shipping paid. We'll buy, 
trade or give you new equipment of your choice. Send 
list or telephone for immediate quote. Payment in 24hrs 

MILITARY ELECTRONICS CORP. 

SPACE ELECTRONICS DIVISION 
4178 PARK AVE., BX. f N. Y. 10457 • (212) CY 9-0300 



WE BUY 



TUBES FOR CASH 

UNITY ELECTRONICS 

107 Trumbull St., ELIZABETH, N.J. 201 - FL 1-4200 



LARGEST SELECTION in United States 
AT LOWEST PRICES — 48 hr. delivery 

Thousands of frequencies in stock. 
Types include HCA/U, HCI3/U, 
FT-241, FT-243, FT- 171, etc, 

SEND I Of for catalog with oscillator 
circuits. Refunded on first order. 

24DQB Crystal Or,. Ft Myers, FJa, 33901 




CRYSTALS 



MARCH 1967 



121 



^— ■ 








•'''"*: w 



^- 



Caveat Emptor? 



KK 



***— 



r~? 



"357 







4* Price— $2 per 25 words for non-commercial ads; $5 
per 25 words for business ventures. No display ads 
or agency discount. Include your check with order, 

it Type copy. Phrase and punctuate exactly as you wish 
it to appear. No all-capital ads, 

it We will be the judge of suitability of ads. Our re- 
sponsibility for errors extends only to printing a cor- 
rect ad tn a later issue. 

it For SI extra we can maintain a reply box for you. 

it We cannot check into each advertiser, so Caveat 
Emptor . . . 



ALL Makes of new and used amateur equipment. 
Write OR call Bob Grimes, 89 Aspen Road, Swamp- 
scott, Mass. Tel: 617-598-9700 or 617-598-2530. 

CONVERTERS. World's largest selection of fre- 
quencies. Ham TV vidicon cameras and parts at 
low factory-direct prices. See them now in our 
full page ad in this issue. Vanguard Labs, 196-23 
Jamafca Ave., Mollis, N.Y*, 11423. 



WE WILL PAY CASH: Wanted, popular, late 
model unmodified amateur equipment. Highest 
prices paid for clean good operating gear. Write 
Graham Radio, Dept. 100. Reading, Massachusetts. 

— ^ 

ARE YOU SINCERE? Are you really looking for 
the best deal on a new or fully guaranteed used 
unit? Let us convince you with a specific quote 
that will really save you money* Graham Radio, 
Dept. 10, Reading, Massachusetts, 



MOTOROLA new miniature seven tube 455 kc if 
amplifier discriminator with circuit diagram. 
Complete at $2.50 each plus postage 50c each 
unit. R and R Electronics. 1953 South Yellow- 
springs, Springfield, Ohio, 

COMPLETE CONVERSION instructions for the 
AN/VRC-2, just $1 While the supply lasts. 73 
Magazine, Peterborough, N. H. 03458, 

WANTED case for Morrow receiver, WA1CCH, 
c/o 73, Peterborough, N.H, 03458, 

Six ASSORTED ISSUES of ATV Experimenter, 
circa '64- f 65, $1 from 73 Magazine, Peterborough, 
N.H, 03458. 



SCHEMATICS FOR either the ARC-508, or the 
AHR 15, both described in June "65 issue of 73, 
only 50c each. 73 Magazine, Peterborough. N.H, 
03458 

1963 BOUND VOLUMES OF 73. $15 each from 73, 
Peterborough, N.H. 03458, 

ROCHESTER, N. Y. is headquarters for Western 
New York Hamfest and East Coast Spring VHF 

Conference, Saturday, May 13. Top programming 
plus huge "flea' 1 market. For more information, 
write: Rochester Amateur Radio Assn., P.O. Box 
1388. Rochester, NY. 14603. 



WANTED: General Radio model 1140A wave- 
meter. W1DTY. RR #1. Box 138, Rindge, N.H. 
03461, 



HANDBOOK OF HAM RADIO CIRCUITS by 

W9CCA. Complete schematics and operation data 
on many popular ham receiver*, transmitter!, 
transceivers and power amplifiers. $2.05 from 73 
Magazine, Peterborough, N.H. 03458. 



CONVERTERS, three transistor, 50-54 m in. 14-18 
mc out wired, tested, printed circuit. Crystal 
controlled. S10 ppd. Tuneable, $8 ppd, Syntelex, 
39 Lucille. Dumont, N.J. 07628, 

25 WORDS FOR *2- Sell or buy through these 
want ads, a terrific bargain. Caveat Emptor, 73 
Magazine. Peterborough, N.H. 03458, 

NOVICE AND TECHNICIAN HANDBOOK by 

W6SAI and W6TNS. Limited quantity for only 
%2 .50 each, 73 Magazine, Peterborough, N.H. 03458 



RTTY GEAR FOR SALE. List issued monthly. 88 
or 44 mH toroids five for $1 75 postpaid, Elliot 
Buchanan, W6VPC, 1067 Mandana Blvd., Oakland, 
California 94610. 

ESTATE SALE and bargain list* Send for it and 
include SASE Write Paradd Sales and Engineer- 
ing Service. 280 Route 10, Dover, N.J. 07801. 



PLASTIC HOLDERS— each display 20 QSL cards. 

3 for $1.00 or 10 for $3.00 prepaid and guaranteed. 
Free brochure of other ham goodies included. 
Tepabco, Box 198N, Gallatin, Tennessee 37066. 

FREE CATALOG— loads of electronic bargains. 
R. W, Electronics, Inc., 2244 So. Michigan Avenue, 
Chicago, Iliiniis 60616. 



DAYTON HAMVENTION April 15, 1967— Dayton 
Amateur Radio Association's 16th annual Ham- 
vention, Wampler Arena Center, Dayton, Ohio. 
Participate in the technical sessions, forums, ban- 
quet and hidden transmitter hunt. Bring XYL 
for best in women's activities. For information 
write Dayton Ham vent Ion, Department C, Box 
44, Dayton, Ohio 45401. 



CHRISTIAN HAM FELLOWSHIP is now being 
organized. For free details write Christian Ham 
Fellowship, Box 218, Holland, Michigan. (Christian 
Ham Callbook $1). 

4*1000 A I G-G all hand final with spare tubes. 3.5 
kW supply, 110-220 input. Both $325. Immaculate 
SW-140. $125. Will deliver either up to 150 miles 
from Bakersfield. Mike Gibson WA6MWA, 3917 
Reno Lane, Bakersfield. California 93300, 

HEATH KIT VHF-1 Seneca transmitter like new, 
120 watts. 6 and 2 meters, Will ship prepaid. Cer- 
tified check, $135. David H. Richardson WA4GNA. 
P.O. Box 213. Demopolis, Alabama 36732. 

COLLINS 75 A2 $185. HT-40 $50. SX-140 $50 and 
SX-100 with speaker $140. All like new. WA7CQX, 
808 East 4th Place, Mesa, Arizona 85201. 



FERRITE BEADS — Modern Slip-On ferromagnetic 
VHF chokes for Parasitic Suppression, HF Shield- 
ing, RF Decoupling and Badioferric Inductors, 
Dozen Beads plus Spec Sheet: $2,00. Packaging 
and Postage: 25c 4 . AMI-TRON Associates, 12033 
Otsego, North Hollywood, Calif. 91607. 

DAVCO DR-30 new model including FETs, $350.00; 
2M Tecraft xmtr l used, $25.00 and new power sup- 
ply, $35.00- Knight 4 track stereo tape recorder, 
used. $75.00: Ed Jurow; 30414 Harding, Olympia 
Fields, Illinois 00461. 



122 



73 MAGAZINE 






UNIQUE relay to build variety of remote controls, 
model railroads, liquid level control, weather de- 
tector, burglar alarm, games, trick circuits. 20 
design ideas included free, 3.95 prepaid. Dept. E„ 
Alco, Lawrence, Mass. 

WANTED: I^ampkin 105-B, 111 PPM Meter, 205A- 
John Crosby, K4GBL, 1421 Bell Terrace. Titus- 
ville, Florida 32780. Condition, age, and price in 
first letter please. 



RADIO OPERATOR — TECHNICIANS NEEDED: 

second class radio-telephone license, some typing 
ability, good character references and diction, 
high school graduate, Illinois State Police Radio, 
777 S. State, Elgin, 111. 60120. 

A UCTIONF EST— Broward ARC— New location this 

year. Chaminade High School. 500 North 51st Ave., 
Hollywood, Florida. March ll t doors open 8:00 
am, auction begins 10:00 am. 

50 FOOT MAST DESIGN. Designed for commer- 
cially available materials. Why pay $360 for a 50 
foot tower? Send $1. Joe Shaw, 2014 Boston, 
Irving, Texas. 

COLLEGE EXPENSES. EICO 753, 751 p.s., factory 
aligned, s,s. VFO, $280. SX-140, $65,; HT-40, $55.; 
HA-5 VFO, 6 mtr. Xtal, $55. All three $165. Webcor 
"Compact Deluxe' 1 Tape Recorder, $65., with 
mike. $70. Turner Dynamic Mike, stand, $14. 
Mosley "El Toro ". (80-40-20-), ?9, Command T-19/ 
ARC-5 Xmtr. $14. WA5JVL. 8704 Belfast. New 
Orleans, Louisiana, 70118. 

JOHNSON RANGER I with PTT\ Johnson Viking 
6-2 transmitter, both excellent condition with 
power cable. $200. WA0AGP. 1139 Crest Drive, 
Topeka, Kansas 66604. 

^ — ™ — ^^^^^^^^^^^^^^^^^^^^^^^^^^^^™-. 

DUMMY LOAD 50 ohms, flat 80 thru 2 meters, 
coax connector, power to 1 KW. kit S7.95 wired 
$11 95 pp HAM KITS, box 175. Cranford, N.J. 

NOVICE CRYSTALS, all bands, SI .30 each. Also 
other freqs. Free list. Dealer and club inquiries 
invited. Nat Stinnette, Umatilla. Fla. 32784. 

HALLICRAFTER SX117 with speaker, like new; 
DX40 Transmitter. VFO, Astatic mike. All per- 
fect $250.00. Never got General license. Pershan, 
WB2HPS 142 Brittle Lane, Hicksville, L.I,, N.Y. 
Tel. OV 1-3145. 

COAXIAL CONNECTORS- Similar to old Genl 
Radio type 774. Set consists of CBWU 49121-A 
plug. CANS 62112 cable adapter and CN 49120 
jack. If you have any of the older model G-R 
test equipment, these are the connectors you 
need, $1,25 each in lots of 10, Large qty avail; 
dealer inquiries invited. K. Y. Hoo. 3233 Conti St. t 
New Orleans, La. 70119. 



WANTED: Copies of 6-UP Magazine, Numbers 5, 
6, 7 and 8 to complete personal collection. Also 
copies of VHFER for 1963 and 1964; April 1965 
also needed. W1DTY, RFD 1. Box 138. Rindge. 
N,H. 03461, 

RHODE & SCHWARTZ type KZS—BN5500 limit 
bridge with all manuals. Like new laboratory 
equipment, WUl sell or swap. Make offer. 
WA5AWO. Box 79 t Port Gibson, Mississippi 39150 



COLLINS, MP-1 and 351D-2 mint condition, 
$175.00, Also crystal bank, contains 126 crystals in 
plastic carrying case, 3.4 Mcs to 30.0 Mcs, $175.00, 
R, C Canter. Rt. #1, Frederick, Md. 2170L 



2NT10G 
M0TOR01 



IGNITION 

transistors 

$-177 

Each 

15 AMP VCB 100 



|So/fd St 



atet 



PNP JOGWett/15 Amp HIPewer 
TOSS Case! 2N44I, 442. 277, 
278, DS501 up U SO Veltt 



2^ ? 



SILICON 
RECTIFIER 



Glass-Sealed 



SALE! 

• GLASS CAPS 

• METALLIZED 



Sale 



Sale PIV 

D 25 * 1400 
39 f 1600 
55c 

D 69t 



Sale 

□ B9t 
1.25 



INTEGRATED 
CIRCUITS 




incline Gatef Q G TOT 
Bi/*fer>.FIiDflot>s $1 89 



ele, Asird, 



li> 



test 



□1 AMP i 
800PIVM 



1 AMP 

Actual Size <— ^ 
MICROMINIATURE 

SILICON RECTIFIERS\ 

PIV Sal* pjV Sale 

50 D 5« 600 n 20 * 
100 □ 7t 800 J 25< 
200 C 94 1000 □ 50* 



lamp 



2000 

PIV 

q 1 $ 1.9 8 

G TRANSISTORS 

100 hr $ 2 98 

Fewer, Audio, IF, unletfed 




AMP TOP HAT AND EPOXIES 



PIV Sale PIV 

50 5* 600 

100 It 800 

200 9* 1000 

400 12c 1200 



Sale PIV S 

20i 1400 1 

25f 1600 1 

50 t 1800 1 

65< 2000 1 




New! 



FRV 

50 □' 
100 
200 I 
300 
400 
500 
600 



SILICON 

CONTROLLED 

RECTIFIERS 

7 16 2b 

AMP AMP AMP 



48 □ 70 
70[jl,20 
1-05Q1.70 
1.60Q2.20 
2.1032.70 
2,80 "J 3.30 
3,00 D 3. 90 



.90 
1.50 

2.10 
2,70 
3,00 
3.80 

4.30 



IEE 

100AMP 

5 RECTIFIERS 

0*i PIV Sole 

rl 50 D 2.59 

100 2.89 

200 3.95 

400 U 5.75 



DC MICROAMMETERS 



QlOOt* EACH 
Volt* Volte Volte 



Volte 

130 
150 
160 

180 
200 



1 AMP 

*oPpiv 



/ / / 



/ MINIATURE 

f4 



for 



*»ART! 



TERMS:* include 



t*g* Rated, net 30 days, COOe 259» 



POLY PAKSHffll 





BOO 

uw 

GOO 

400 

11)0 

100 

50 

50 

50 

SCR 



TOP HATS, EPOXIES, STUDS, SOU'S 

PIV 1.5 Amp Epoxy 69c 5 for $3,00 

PIV 1.5 Amp Tophat .......59b 5 for 2.5D 

PIV I. Amp Tophat 39n 5 far 1.75 

PIV I. Amp Tophat ,..29e 4 for 1,00 

PIV 6. Amp Tophat, ,.39o 5 for 1.75 

PIV .2 Amp Tophat. ......15c 8 for 1.00 

PIV 150. Amp Stud..... ....12.95 4 for 10.00 

PfV S. Amp Stud ........980 5 for 4.5Q 

PIV .5 Amp Tophat .15* 8 for 1.00 

Gen, Ele*. G40B (2H6S5) 200 PIV 25A. ....... ..2.95 



ARROW SALES-CHICAGO, INC 

2534 S. MICHIGAN AVENUE 
CHICAGO, ILLINOIS 60616 



QUAD AND BEAM BREAKTHRU 

QUADS: PROVEN SENSATIONAL! All metal fescept spacing 
insulator dowels) ; full size; two element; absolutely complete 
with sted boom; all hardware; wire and flttlngs; terrific gain 
and directivity; one man installation; no bamboo or fibregkss; 
all quads use single 52 ohm coaxial f eedllue : 10-15-20 Quad, 
$35; 15-20 Quad, $32; 10-15 Quad, $30' 20 Meter Quad ( 
$25; 15 Meter Quad, $24; 10 Meter Quad, $23, 
BEAMS: new complete with boom and hardware; 8WR Id; 
bamftes 5 KYV; adjustable entire band; %" and 1" alum. 
alloy tubing; single coaxial feedline: 



4 EI 20 

3 EI 20 

2 El 20 

5 EI 15 

4 EI 15 

3 EI 15 



. . 



•r • • • 



* * « 



**..« + ** 



steel boom 



$12. 

28.* 

15. 
32.* 

15. 



$32.* 
22.* 
16. 

2S.* 

25,* 

16. 

ALL BAND VERTICAL VSO [6 thru SO) .$16.95 

ALL BAND VERTICAL V160 (6 thru 1U0) 18.95 

Ki-mll with order; shipped charges collect. 
GOTHAM, 1S05 Purdy Aie. f DepL 73, Miami Beach, Fla. 33139 



2 EI 15 
6 EI 10 

4 EI 10 
10 EI 6 
4 EI 6 

*Has 20' 



LEARN RADIO 



THE EASY WAY! 

* Ho Books To Read 

* No Visual Gimmicks 
To Distract You 

* Just Listen And Learn 

Based on modern psychological 
techniques— This course will take 
you beyond 13 w.p.m* In 
LESS THAN HALF THE TIMEI 

Album contain! thrt© IS* Also ovailabfe on magnetic tap** 
LPs 2ft hr. instruction s ee your dealer nowl 



EPSILON [£] RECORDS 



206 East Front Street, Florence* Colorado 



GUARANTEED RECONDITIONED 




rf&tftftd 



Dl 2-5757 



HAM GEAR 

WRITE NOW 
FOR MONTHLY 

FLYER. 



999 HOWARD A VE-BURLTNGAME, CAL, 



HERE'S A PERFECT MATCH 

Now you can get a perfect match for Hy Gain two- 
meter models 23, 28 and 2 IS. This fs an L-matcH ar* 
rangement that gives LOS to 1.00 SWR at the antenna. 
Only $2.50 ppd. Send for the L-Match to: 

Sound and TV Systems 

116 Mariemont Drive, Lexington* Ky. 40505 



PLASTIC GALL 6V NAME BADGES. Money Back 
Guarantee. Slip-on shirt or suit pocket. Your call 
plus up to 10 engraved permanent white letters 
on 1" jl Z" black background. $1.00 postpaid. 
W0KSL, 606 N. Main, Stlinwood, Kansas. 



HALL I GRAFTERS SX-101 NIK 1 1 1, $140.00; MT-40, 
$35.00; homebrew six meter kilowatt, rack mount- 
ing with three meters, $40,00. Ship REA collect. 
Andrew Borsa. WA1FRJ, 977 Westford St.. Lowell, 
Mass. 01851. 

HT-32A, HQ-170, Both in good condition, $420.00. 
Also DX-40 and VF-1. Need money for college 
expenses. Ken Eigsti K90FB, Route 2 t Morton, 
Illinois 61550, 

NEW AMECO CODE OSCILLATOR, $14. Variable 
capacitors. Hanimarlund MC-140-3 52.00. Bud 1876. 
$1.65. both 140 pf. Plus postage. Norman Ruseh, 
2222 Newberry Avenue, Green Bay. Wisconsin 

54302. 

. ■ 

TEN METER SIGNAL GENERATORS, $5.95 each. 
Postpaid. Crystal controlled tone modulated. On 
PC board. 2x5 inches. Like new. Tested. Your 
choice in 10 kHz steps. 28.615 to 28.905 MHz Less 
battery and switch. Specify frequency. Sorry, no 
COD. Wayne Lafayette, 5429 North Detroit St., 
Toledo, Ohio 43612, 

WRL's used gear saves money! Reconditioned - 
guaranteed-trial. Free list. Special! My personal 
antenna 'farm". One package , $1,000. 2 Aeromotor 
70* towers, 1 each Telrex 10, 15, 20 beam 6 element 
and 1 HyGain 3 element 40, 2 rotors. Write for 
details. Leo, WOGFQ, Box 9l9 t Council Bluffs, 
Iowa 51501. 

HALLICRAFTER SR 160 transceiver $175.00. Orig- 
inal standard Vibroplex $12,00. Heath HD19 phone 
patch $20,00. Workshop ten meter beam $10 00. 
(Beam local only), W. F. Walsh W2BTE 368 Dur- 
ham Court, Union, N.J. 07083. 



GOOD KW-32 and HF-23 for $100; DX-40 with 
built-in antenna relay, $30; Vanguard 6 meter 
converter (New) $5; K0MVR, 424 Twentieth Street 
N.E., Cedar Rapids, Iowa 52402. 



BARGAIN! Ameco TX-62 with relay $100 match- 
ing 621 VFO |25. SX-110 Rcvr. with Q mult. $50. 
Shure Unidyne m mie. $25. WB2VHW Call f212) 
449-4326, 

NEW AND EXCELLENT reconditioned equipment 
at lower prices. Te-ms. Collins 75S-3 T 32S-3, 
KWM-2; Drake 2-B. T-4X; Gonset GSB-101, GSB- 
201; G-50, Hallicrafters SX-1I0, SX-lil, SX-101A, 
HT-37, SR-160. SR-150; Hammariund HQ-150, HQ- 
170, HQ-170A; National HRO-GO. NC-303. NCX-3, 
NCX-5, NCL-2000, NC-183. Much other equipment 
Write for price lists, Henry Radio Company, 
Butler, Missouri, 

WANTED— Teletype 28s, parts, what have you. 
SELL— machines, parts. Fred Schmidt. W4NYF, 
405 NW 30th Ter., Ft. Lauderdale, Fla. 33311. 305- 
583-1340 (9 P.M, EST.) 

TOOOOBES: SUA— $4.25; 7094— $26.90; 6146A— $2 25; 

6CW4— $1.40; 5894 — $15.50; Extra power 6146B — 
$4.00; 6360—53.45; 8236— S9.50. All new, boxed, guar- 
anteed. FREE catalog VANBAR Distributors, Box 
444Y. Stirling. N.J. 07980, 



73 MAGAZINE 






SIX METER EQUIPMENT Clegg Venus and Na- 
tional FS, $400, Clegg SSB booster, $50, Electro- 
Voice 664 microphone, $30, Bendix Microw Match 
SWR Bridge, $25, Heath monitor scope, $40, AH 
of the above In one package If possible. 100TH 
linear with PS. Variac, 0-3500 volts, at 1 amp- 
No TVI, SI GO. Five element Telrex and AR22 
rotator, $60. Two meter Poly Comm transceiver, 
5160. All above equipment in excellent condition. 
Joseph Ciadi, 106 Maple Street, Weehawken, N.J. 
UN 3-0290. 

NEATH KIT dc power supply HF13> $50. R. Steph- 
ens W2NTZ, 3048 Wilson Avenue, Bronx, N,Y. 
10469. 

SWAP: 120-base, mother of pearl Wurlitzer ac- 
cordian for HQ-1S0AX, SX-115 or RTTY gear. 
John Waskowitz, 541 Marcy Ave,, Brooklyn, N.Y. 
11206. 



APACHE, TX-1, Excellent, not a scratch, best 
offer: AF-67, FMR-7 transmitter- receiver, with 
supply, converted 6 through 80, best offer, K1FNI, 
133 Larchmont KcL, Warwick, R.I. 02886. 

SELLING OUT large collection of AM and FM 
gear, going SSB. Send stamped envelope for list. 
Warren Waterman W2JRX, Middletown, N.Y. 
10940. 

DRAKE 2B, calibrator, low frequency converter, 
speaker. Q multiplier. $240, Heath KW amplifier. 
Original owner of both t like new. Nick r 5750 
Yukon, Sparks, Nevada 89431. 

i 

SWAN 25Q, 110 vac power supply and speaker, 
crystal calibrator, S meter, and audio control. 
New condition, $400, WB6SML, phone 714-278-9442, 
2430 Galahad Hd., San Diego, Cal. 92123, J. Horgan. 

QSL CARDS???? America's Finest. Samples 254, 
Deluxe samples, 35tf, Sakkers Printery, W8DED, 
Holland, Michigan. 

GREAT BAYS catalog 10<. Electronic, electro- 
mechanical bargains. AUdio output transformer 
6L6"s match $2.95. Gear bonanza 3 lbs, per pack- 
age. $2.00, Fertik's* 5249 D, Philadelphia, Pa 19120. 

DX-60 ?55, HG-10 VFO $25, NC 109, $80. All excel- 
lent condition with manuals and extra tubes. 
Wanted: phone patch. Stephan Budensiek, Rt* 2, 
Salem, Ohio 44460. 



SELL KW RKGSs GG linear, commercial cabinet 
no supply. $95. Power supply, 1000, 1250, 1500 
switched, 525. SRI 60 with both supplies, 40 meter 
Hustler antenna, perfect, S350. L. E. Lane, 922 
Mount Ranier Way, EI Dorado Hills, Calif. 95630. 

TRANSMITTERS, RECEIVERS REPAIRED. Align- 
ment, calibration, kits wired. Work done by li- 
censed engineer. All lab test equipment. J and J 
Electronics, Windham Road, Canterbury, Conn. 

06331. 



TELREX 20M-317R. Excellent condition, $85. 710 
Arnold, Alamogordo, New Mexico 88310. 



QSL CARDS. Free samples, 
lope to George WA4QKD, 
Florida 32580. 



Send stamped enve- 
Box 282, Valpariso, 



HALLICRAFTERS SX110 receiver, perfect condi- 
tion, general coverage with ham bandspread, 
crystal filter $90, Local only. Pullman, 758 Brady, 
NYC, 597-A293. 




MAY 13 

Rochester, N.Y. 

V1NCES SO ACRES 

WESTERN N.Y. HAM FE ST and 

EAST COAST SPRIN6 VHF CONFERENCE 

ROCHESTER AMATEUR RADIO ASSOCIATION 
P. O BOX 139S ROCHESTER. N. Y . 14603 



BLOWER 

MOTOR 



IWsrO, 117*. 60 cycle* .65A. 1700 

RPAI: Dual 5/Ifi* shaft, 1-3/4* 

& 3/1*, 4 mounting studa, 2* $4.50 ea. 

center*. Quiet NEW. 6 pounds 

shipping wL 



IMPELLER 
HOUSING 

COMBINATION 



813 TUBE 
SOCKET 



6-24 PF DUAL 
3500 v 



PL-259A 
M-Mt 

1625 
SOCKET 

IN-34A 



2-3/4" difl. 1-7/8" deep. BAL- 
ANCED. Fits 5/iS" shaft. With 
housing, takes 2* nozsle. Bit AND 
NEW. 2 pounds shipping wt. 

Both above, (no mounting bracket 
■Tillable). 

7 pin giant ceramic wafer, EFJ 
r 122-217-201 (military). BRAXD 
NEW, 4/$3.75. 

Variable capacitor. Very heatr 

silver plate, la que red. Split stater $2.00 ta. 

on mica tilled base. Dual 1/4* 

abaft, 1/2* Sc 1/4* long. BRAND 

NEW. 1 pound. 4/$7,50. 



$1.75 ta. 

$5.75 art 
SL00 



3 piece, UHF co- ax 
PLUS. Discolored. 



mala SUR 



4/S1-10 
29« 



H. iinKld T7HF adapter, SUR- 
PLUS. Discolored. 

\2\\ 7 pin, SOT tubes. BRAND 
NKYV. Min, order. 

7 pin large, for 162.S37. 3AP1. 
EFJ -122 227. 

i ;<»nu8nium diodev Untested term* 
inution. Avenge 50 to &Q% good, 
AS IS. Minimum order. 



3/SI.I0 

39c a*. 



8/ $2.20 
4/SI-I0 

30/S2.00 



Alt orders, except in emergency, or I'm at a Manifest, 
shipped same day received. For fre« h " GOO Dili;" sheet, send 
self -addressed, stamped envelope — PLEASE, PLEASE include 
sufficient for postage, any excess returned with order. I carry 
private (Traveler 8) parcel post insurance, for domestic parcel 
post. For items too heavy, or too large for parcel post, 
I suggest bus parcel express. Please advise name of bus 
line, and city, where you can pick up the shipment. 

B C Electronics 

Telephone 312 CAIumet 5-2235 
2333 S. Michigan Avenue Chicago, Illinois 60616 



MOVED TO LARGER STORE 



Many More Parts and Equipment 
We Invite Your Inspection. 

DOW TRADING CO., INC. 

1829 E. HUNTINGTON DRIVE HY. 66 
DUARTE, CALIF. 91010 PHONE 357-3763 



TRANSMITTERS— RECEIVERS: 



BC-453 Receiver— I TO to 550 KC ..........Used; $16.95 

BC-455 Receiver— 6 to 9 MC- 

Gov't. Reconditioned, w/Dyn,: 

BC-456 Modulator ...Used: 

BC-696 Trans.— 3 to 4 MC, Gov't Recond.: 

T-20 Trans. — 4 to 5.3 MC ... ¥ ^ New: 

T-21 Trans. — 5.3 to 7 MC , . , .New: 

T-22 Trans.— 7 to 9 MC „ „„New: 



14,95 
3,95 

12.95 
9.95 
9.95 

18.95 



BC-348 Receiver— 200 to 500 KC— 

1.5 to 18 MC_ 



..Used: 69.50 



Send 25t (colas or stamps) for 
NEW CATALOG? — your copy & receive 50* credit 

on your order* 

Prices F.O.B., Lima, O* • 25% Deposit on C.O.D.'s • 
Minimum Qrdar 55 

FAIR RADIO SALES 

DEPT. 73, P. O. Box 1105, LIMA. OHIO 45802 



■ 



LIBERTY ELECTRONICS WANTS TO 



FOR CASH 



Electron tubes and 
semiconductors 

Most any type or quantity 

Receiving, transmitting) special 

purpose, magnetrons, klystrons 

We will make you an immediate 

offer in cash. 



Special sale 

HP-200BR audio 
oscillator $65 



Surplus communication and test equipment 

AN/GRC-3, 4, 5, 6, 7, 8, 10, 19, 26, 27, 46, VRC-12 

AN/PRC-8. 9, 10, 25 

Test equipment with ARM, SG, URM, UPM, USM, and TS prefixes 

Communications: AN/TRC-1, 24, 35, 36 

Receivers: AN/APR-9, 13, 14, R-388A, R-274, R-390A, R-391, etc. 

Indicators: ID-250, 251, 387, 257 A, etc. 

Aircraft; AN/ARC-27, 34, 38, 44, 52, 55, 57, 73, 04 

AN/ARN-14, 59, 67, 70 
AN/APS-42, 81 
AN/APN-1, AN/CPH-2A 

Also: Tektronix, Hewlett Packard, Boonton, and General Radio 
equipment, etc. 



Liberty Electronics, Inc. 

548 Broadway, New York, New York 10012, Phone 212-925-6000 



SPACE AGE KEYER 




Planar epitaxial integrated circuits for reli- 
ability. No tubes — No separate transistors. 
Precision feather-touch key hvitt-in. 
Fully digital — Dot-dash ratio always per- 
fect. 

No polarity problems — Floating contacts 
switch 1-amp. 

Rugged solid construction — will not walk. 
Send QSL or postcard for free brochure. 



INDEX TO ADVERTISERS 



BOX 455, ESCONDIDO, CAL. 92026 



Ameco, 109 
American Crystal, 120 
Amrad Electronic, 124 
Antenna Mart, 103 
A.R.C. Safes, 120 
Arrow Sales, 124 
Atlantic Surplus, 118 
A.T.V. Research, 109 

B C Electronics. 125 
Barber Travel, 1 18 

Callbook Magazine, 110 
Ceveland institute, 117 
Columbia Electronics, 121 
Confide!, Inc., 45 
CTK's Barb'd Wire Ant. t 

114 
Cush Craft, 113 

Peter W. Dahl Co., 120 
Ted Dames Co,, 120 
Day co Electronics, 31 
Dayton Hamvention, 22 
Dixon's Radio Key, 111 
Dow Trading, 125 
DPZ, Inc., 114 
R. L> Drake Co., 17 

Editors & Engineers, 111 
Electronic Center, 97 
Epsilon Records, 124 
Evans Radio, 113 

Fair Radio, 125 

Galaxy Electronics, 

Cover I if 
General Surplus, 118 
H. Vv\ Gordon Co., 101 
Gotham, 124 
Heath Co,, 35 



Henry Radio, 63 

International Crystal, 3 
Invertronics, 120 

James Research, 117 
JAN Crystals, 121 

Liberty Electronics, 126 

Meshna 119 
Midway Antenna, 121 
Military Electronics, 121 
Mission Electronics, S5 
Mosley Electronics, 19, 39 

National Radio Co., 

Cover IV 
New-Tronics Corp., 23 
Norman Electronics, 115 

PoloTiar Engineers, 126 
Parks Electronics, 120 
Poly-Paks, 123 

Ro^in Mfg. Co., 16 

Solid State Sales, 127 
Sound & TV, 124 
Southwest Semicond., 117 
Swan Electronics, 27 

TAB, 115 

Technical Topics, 109 
Telepiex, 108 
Teirex. 99, 112 

Unity Electronics, 121 

Vanguard Labs., 104, 105 
VHFer. Ill 

Waters Mfg. Co., 5 
Western N.Y. Hamfest, 125 
R. & C. Wilson, 118 
World Radio Labs*, 43 
73 Books, 59 
73 Subscriptions, 97 



4$± 

OTA 

L A L 
I 
D 




INTEGRATED CIRCUITS ARE NOW AVAILABLE 

JK FNp Flops „.__.. . „__ $1.15 

Dual Nand-Nor gates S I 00 

GUARANTEED TO WORK 
TO-85 flat pack case. They come complete with sche- 
matic electrical characteristic sheet and some typical 
applications, $?. 00-$ 1 5. 00 values from original manu- 
facturer. We have other types of IC's In these series 
available* Send requests. 




6"x9" speakers, 20 ohms, 1.5 oz magnet 

4" speaker, 3.2 ohms, 1 qz magnet 

2,5" speakers, 10 ohms 

Dual 1 megohm potentiometers with 6 and 12 

volt off -on switches 
455 KC IF transformers double slug transistor typi 
262 KC IF transformers double slug tube type 
Dual 20 MFD at 350 volt electrolytic condensers 
28-101 MMF ceramic trimmer condensers 
GaAs Varactors, similar to AP-1, AP~6 P etc. 70 

KMC at 150 mw. 



TRANSISTORS 

NPN dual transistors. A TO-5 pack* 
age (2N2060) containing two high gain 
100 MHz silicon NPN transistors. 

$1.50 
PNP dual transistors, A TO-5 package 
(2N2S07) containing two high gain 
100 MHz silicon PNP transistors. 

$1,50 
NPN high vo'tage transistors. 150 
VBCO at 2.5 A with a high gain in 
a TO-66 package. $1.50 

PNP silicon epitaxial low leakage 
transistor m TO-1S package. Similar 
to 2N2185 30 volts at 150 mw. 

3/$ 1.00 
Similar to 2N329A general purpose 

PNP epitaxial transistor in TO-5 pack. 
Low leakage 30 volt unit with a 400 
mw dissipation rating and B 30-80. 
Comp, with a $9 value. 4/$ 1.00 

Similar to 2N3060, a 60 volt silicon 
PNP in TO-46 pack has a S of 30 
with 4 W dissipation. Used in DC 
amplifiers, high voltage work and 
audio systems. 4/$ 1.00 

Similar to 2N1640 bidirectional trans* 
istor, a TO-5 silicon unit, in which 
the emitter and collector are inter- 
changeable. 75* each 
Similar to 2N339-2N341, etc. High 
voltage medium power units, NPN 
s if icon. 7/$ 1.00 
Similar to 2N72S. A high frequency 
NPN TO-18 unit extending to the 
UHF range. 3/$1.00 
Similar to 2N545, a 5 watt NPN TO-5 
high voltage unit used for last switch- 
ing, 5/S1 00 
Similar to 2N1648 NPN high voltage 
20 watt silicon unit used in power 
output stages and power transistor 
drivers. 75^ 
Simifar to 2N2875 PNP silicon 20 
watt power transistor with cut off 
frequency to 30 mc. 75e 
Similar to 2N2885 NPN and TMT8035 
PNP microtransistors. 75 mw power 
at high frequencies. Both units $1.00 



$2.50 each 

1,25 each 

2/51.00 

4/J1.00 

i 3/J1.00 

3/$1.00 

40* each 

6/$ 1.00 

$4.00 each 



TOP 


HAT & 


EPOXIES 


PRV 


750MA 


100 


.07 


200 


.09 


400 


.12 


600 


.20 


800 


« £* *J 


1000 


,50 


1200 


.65 


1400 


.85 


1600 


LOO 


1800 


1.15 



Silicon Power 

Rectifiers 

PRV 40A 240A 

100 1.00 5.00 
200 1.50 7.50 
400 2.00 15.00 
600 2.50 20 00 
mo 3.00 
1000 4.00 35.00 



5A Insul 




Base 




PRV 






200 




.40 


400 




.60 


600 




1.00 


800 




1.25 







CONTROLLED 




i 


SILICON 




RECTIFIERS 




PRV 




7 A 


20 A 


50 




,50 


,80 


100 




.70 


1.35 


200 




1.05 


1.90 


300 




1.60 


2.45 


400 




2.10 


2-85 


500 




2,80 


3.50 


600 




3.00 




700 




3,50 





Similar to 2N247 PNP germanium- 
Good for rf work, 10/$ 1.00 
Similar to 2N255 20 watt PNP ger- 
manium power transistor in TO-3 
case 4/1 ,00 
Similar to 2N327A PNP silicon TO-5 
unit used in audio, 6/$1.00 
Similar to 2N519 silicon PNP unit 
used in rf circuits. 10/$1.00 
Similar to 2N389, 424, etc wat 
high voltage NPN silicon 
TO-53 case. 

Similar to 2N1209, 2N1212, etc., with 
similar electrical characteristics In 
11/16" stud package. 75* each 

FET'S N channel type similar to 
C610 used as amp, switch, chopper — 
very high input 2, $1.50 each 



unit in 
75* each 



DIODES 



10 watt zeners, 2-180 volts, state volt- 
ages desired. 75* each 
1N429 6 volt double anode regulator. 
2 watts. 5/$1.00 
SV176 7 volt reference diode 5/$1.00 
Silicon bilateral switch. Replaces two 
SCR's by firing in either direction 
when breakdown voltage exceeded. 
Used \n light dimmer*, etc. 75* 
Silicon voltage references* These are 
a series of precision regulators de- 
signed to operate from 2 volts up. 
similar to SV140, SV3207, etc. 50* 
1N251 a high frequency silicon diode 
used to 1000 mc. May be used as 
discriminator or detectors. PIV of 20 
vo'ts 10 $1,00 
S284 similar to 1N251 but with PIV 
of 30 volts, 10/$ 1.00 
Glass diodes. Color coded Si 20/$100 

Ge 30/$ 1.00 
Micodiodes similar to MD27, etc.. up 
to 200 PIV at 30 ^a- These are switch* 
ing diodes with a short recovery time 
03 /isec). 6/$ 1.00 

High voltage assemblies, 3000-6000 V 
at 150-200 mils. These silicon assem- 
blies may be put in series to achieve 
higher voltages. $1.50 



SOLID 
STATE 




SEND 20c FOR CATALOG 

TERMS: FOB Cambridge, Mass, Send check or money order, in- 
cluded postage, average wt. per package Vz lb- Allow for COD. 
Minimum order $3.00. 

P.O. BOX 74C, SOMERVILLE, MASS. 02143 



THE HE IV 



GALAXY 




MARK 2 



5 BAND TRANSCEIVER MOBIU » 



FIXED STATION 



NOW --even Better than Ever! 




YOU CANT MATCH ALL THESE FEATURES 
ANYWHERE. ..AT ANY PRICE! 







These NEW Features... Plus all the great features that put the 

GALAXY V in a CLASS by ITSELF! 



• New 400 Watt Power 

• New Precise Vernier 

Logging Scale 

• New Solid-State VFO 

• New CW Sfdetone Audio 

• New CW Break-In Option 

• New CW Filter Option 



• Smallest of the High-Pow- 
ered Transceivers, (6"xi0i4" 

* Great for either Mobile or 
Fixed Station. Xo compro- 
mise in power. 

■ Holiest Receiver of any 
Transceiver — Special New 
Six-Crvstal lattice filter. 



• Complete 80-10 Meter Cov- 
erage. 500 KC on all bands, 
with 1 Megacycle on 10 Me- 
ters. 

• Both Upper and Lower Se- 
lect ible Sideband, 

•Highest Stability. Drift Less 
than KM) CY in any 15 min- 
ute period after wamnup. 



• The personal drift chart of every Galaxy that comes 
off our line goes with the unit to its new owner! 



Write for free Brochure* complete specs on the GALAXY V MARK 2— 

GALAXY ELECTRONICS 

Pacesetter in Amateur/Commercial Equipment Design" 
10 South 34th Street • Dept. 73-I5R • Council Bluffs, Iowa 51501 






New from National 

The most versatile 
5-bander on the market 

. . . priced even lower 
than a kit rig! 







Here's the fastest way to move up from single 

band or triband operation * * . the all-new National 200, It's a 

fabulous five-bander, an ideal rig for mobile, portable, or home operation . . . and it's only 

$359! For the first time at this amazingly low price, you get top-notch SSB, CW, and AM 

performance on the 80 through 10 meter bands . . . plus National's traditional quality and 

full One- Year Guarantee. 

Only National gives you these important features: ■ Complete coverage of the 
80 through 10 meter bands. ■ 200 Watt PEP input on SSB, plus CW and AM. — Separate 
product and AM detection plus fast-attack slow-release AGC. ■ Crystal-controlled front 
end and single VFO for high stability, and identical calibration and tuning rate on all 
bands. ■ Crystal lattice filter for high sideband suppression on transmit, and rejection of 
adjacent QRM on receive . . . plus solid-state balanced modulator for "set-and-forget" 
carrier suppression. ■ Operation from new low-cost AC -200 supply or from NCX-A or 
mobile power supplies. ■ ALC. ■ 45/1 planetary /split gear tuning 1fc1^% F am f\ 
drive, ■ Automatic carrier insertion in AM and CW modes, ■ Panel _ *P ^*^^J 



meter automatically switched to S-units on receive. ■ Universal ONLY 



mobile mount included. 



with National's full 
One-Year Guarantee 



<ss*> National Radio 

*"S 57 Wnehinortrm Sfr^of Moli 



37 Washington Street, Melrose, Massachusetts 02176